Robot arm apparatus, robot arm apparatus control method, and program

ABSTRACT

A robot arm apparatus according to the present disclosure includes: one or a plurality of a joint unit that joins a plurality of links constituting a multi-link structure; an acquisition unit that acquires an on-screen enlargement factor of a subject imaged by an imaging unit attached to the multi-link structure; and a driving control unit that controls driving of the joint unit based on a state of the joint unit and the enlargement factor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of U.S. application Ser.No. 15/126,552, filed Sep. 15, 2016, which is a national stageapplication of International Application No. PCT/JP2015/058568, filedMar. 20, 2015, which claims priority to Japan Application No.2014-069790, filed Mar. 28, 2014, the entire contents of each of theabove are incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a robot arm apparatus, a robot armapparatus control method, and a program.

BACKGROUND ART

Recently, in industrial fields, robot apparatuses are being used widelyto perform work more accurately and more quickly. Some robot apparatusesare made of a multi-link structure in which multiple links are joined toeach other by multiple joint units, and by controlling rotationaldriving in the multiple joint units, the driving of the robot apparatusas a whole is controlled.

Here, position control and force control are known as control methods ofthe robot apparatus and each of the joint units. In position control,for example, a command value such as an angle is provided to an actuatorof a joint unit, and driving of the joint unit is controlled accordingto the command value. Meanwhile, in force control, a target value offorce applied to a task target by a whole robot apparatus is given, anddriving of a joint unit (for example, torque generated by the jointunit) is controlled such that the force indicated by the target value isimplemented.

Generally, most robot apparatuses are driven by position control sinceit is convenient to control and a system configuration is simple.However, position control is commonly called “hard control” since cannoteasily deal with external force flexibly, and position control is notsuitable for a robot apparatus performing a task (purpose of motion)while performing physical interaction (for example, physical interactionwith a person) with various external worlds. Meanwhile, force controlhas a complicated system configuration, but can implement “soft control”of a power order, and thus force control is a control method suitable,particularly, for a robot apparatus performing physical interaction witha person and a control method having excellent usability.

For example, with regard to an example of a robot apparatus applyingforce control, Patent Literature 1 discloses a robot apparatus thatincludes a movement mechanism configured with 2 wheels and an arm unitconfigured with a plurality of joint units, and performs control suchthat the wheels and the joint units are driven in a cooperative manneras a whole (performs whole body cooperative control).

In addition, with force control, there is demand to detect moreaccurately the torque in each joint unit of the robot apparatus(including the generated torque generated by the joint unit and theexternal torque imparted to the joint unit externally), and performfeedback control and/or feed-forward control. For example, PatentLiterature 2 discloses a torque sensor that, by including a splitstructure (decoupled structure), realize accurate torque detection withthe influence of vibration decreased as much as possible.

Also, Patent Literature 3 below describes a technology that uses asurgical microscope adopting a structure with a balanced center ofgravity to thereby enable operation with a light operating force.

CITATION LIST Patent Literature

Patent Literature 1: JP 2010-188471A

Patent Literature 2: JP 2011-209099A

Patent Literature 3: JP 7-16239A

SUMMARY OF INVENTION Technical Problem

In recent years, in the medical field, attempts to use a balance arm(also referred to as support arm) in which various medical units (frontedge units) are installed at a front edge of an arm unit when variousmedical procedures (for example, surgery or an examination) areperformed have been made. However, with a typical balance arm, since thearm is balanced, the arm will move in response to a light force, makingit to operate with slight amounts of movement, and also making itdifficult to ensure freedom of imaging, such as imaging from a varietyof directions in a state in which the imaging site is locked to acertain site on the patient's body, for example.

In light of the above circumstances, as a device to replace a balancearm, there is also proposed a medical robot arm apparatus whose drivingis controlled by position control in order. However, in order to moreefficiently perform a medical procedure and reduce a burden on a user,high operability enabling more intuitive control of a position orposture of an arm unit and a front edge unit by a user is necessary fordriving control of a robot arm apparatus. In a robot arm apparatus inwhich driving is controlled by position control, it is difficult to meetsuch a user demand.

Given circumstances like the above, it is desirable to realize a robotarm apparatus enabling optimal operation according to user demand.

Solution to Problem

According to the present disclosure, there is provided a robot armapparatus including: one or a plurality of a joint unit that joins aplurality of links constituting a multi-link structure; an acquisitionunit that acquires an on-screen enlargement factor of a subject imagedby an imaging unit attached to the multi-link structure; and a drivingcontrol unit that controls driving of the joint unit based on a state ofthe joint unit and the enlargement factor.

According to the present disclosure, there is provided a program causinga computer to function as: means for detecting a state of one or aplurality of a joint unit that joins a plurality of links constituting amulti-link structure; means for acquiring an on-screen enlargementfactor of a subject imaged by an imaging unit attached to the multi-linkstructure; and means for controlling driving of the joint unit based ona state of the joint unit and the enlargement factor.

According to the present disclosure, there is provided a robot armapparatus including: one or a plurality of a joint unit that joins aplurality of links constituting a multi-link structure; and a drivingcontrol unit that controls a viscosity of driving of the joint unitbased on a state of the joint unit.

Advantageous Effects of Invention

According to the present disclosure, it is possible to realize a robotarm apparatus enabling optimal operation according to an image capturedby an imaging unit.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram for describing an application exampleof using a robot arm apparatus according to an embodiment of the presentdisclosure for a medical purpose.

FIG. 2 is a schematic diagram illustrating an external appearance of arobot arm apparatus according to an embodiment of the presentdisclosure.

FIG. 3 is a cross-sectional diagram schematically illustrating a statein which an actuator of a joint unit according to an embodiment of thepresent disclosure is cut along a cross section passing through a rotaryaxis.

FIG. 4A is a schematic diagram schematically illustrating a state of atorque sensor illustrated in FIG. 3 viewed in an axis direction of adriving shaft.

FIG. 4B is a schematic diagram illustrating another exemplaryconfiguration of a torque sensor applied to the actuator illustrated inFIG. 3.

FIG. 5 is an explanatory diagram for describing ideal joint controlaccording to an embodiment of the present disclosure.

FIG. 6 is a functional block diagram illustrating an exemplaryconfiguration of a robot arm control system according to an embodimentof the present disclosure.

FIG. 7 is a schematic diagram illustrating a configuration of a specificsystem that adjusts a usability of a robot arm according to a zoomfactor.

FIG. 8 is a schematic diagram illustrating an example of a map to usewhen a central processing unit computes a viscosity according to a zoomfactor.

FIG. 9 is a flowchart illustrating a processing procedure of a robot armcontrol method.

FIG. 10 is a flowchart illustrating a process of control according to azoom factor.

FIG. 11 is a schematic diagram for describing operation of a robot armthat matches on-screen directions.

FIG. 12 is a flowchart illustrating a process of operating an arm unitto match the on-screen XY directions illustrated in FIG. 11.

FIG. 13 is a functional block diagram illustrating an exemplaryconfiguration of a hardware configuration of a robot arm apparatus and acontrol device according to an embodiment of the present disclosure.

FIG. 14 is a schematic diagram illustrating an example of a map to usewhen a central processing unit computes a velocity and an amount ofmovement according to a zoom factor.

DESCRIPTION OF EMBODIMENT(S)

Hereinafter, (a) preferred embodiment(s) of the present disclosure willbe described in detail with reference to the appended drawings. In thisspecification and the drawings, elements that have substantially thesame function and structure are denoted with the same reference signs,and repeated explanation is omitted.

The description will proceed in the following order.

1. Review of medical robot arm apparatus

2. Embodiment of present disclosure

2-1. External appearance of robot arm apparatus

2-2. Generalized inverse dynamics

2-2-1. Virtual force calculating process

2-2-2. Actual force calculating process

2-3. Ideal joint control

2-4. Configuration of robot arm control system

2-5. Specific example of purpose of motion

3. Control according to zoom factor

4. Processing procedure of robot arm control method

5. Operation matching on-screen directions

6. Hardware configuration

7. Conclusion

<1. Review of Medical Robot Arm Apparatus>

First, to further elucidate the present disclosure, the backgroundleading up to the inventors' conception of the present disclosure willbe described. For example, a method is proposed in which a unit havingany of various imaging functions, such as a microscope, an endoscope, oran imaging unit (camera), is provided as a front edge unit on the frontedge of an arm unit of a balance arm, and the practitioner (user)performs various medical procedures while observing an image of anaffected area captured by the front edge unit. However, the balance armhas to be equipped with a counter balance weight (also called a counterweight or a balancer) for maintaining balance of force when the arm unitis moved and thus a device size tends to increase. A device used in amedical procedure has to be small in size since it is necessary tosecure a task space for the medical procedure, but it is difficult tomeet such a demand in general balance arms being proposed. Further, inthe balance arm, only some driving of the arm unit, for example, onlybiaxial driving for moving the front edge unit on a (two-dimensional)plane is electric driving, and manual positioning by the practitioner ora medical staff therearound is necessary for movement of the arm unitand the front edge unit. Consequently, with a typical balance arm, it isdifficult to ensure consistency during imaging (such as the positioningaccuracy and vibration damping of the front edge unit, for example),such as imaging from a variety of directions in a state in which theimaging site is locked to a certain site on the patient's body, forexample. In addition, if an imaging unit such as a camera is mounted tothe front edge of a robot arm apparatus, in some cases a subject imagecaptured by the imaging unit is displayed, and the operator operates therobot arm apparatus while checking the captured subject image.Additionally, if the imaging unit includes a zoom function, the degreeof minor adjustment of the robot arm by the operator is differentbetween the case of increasing the imaging magnification of the subjectand the case of decreasing the imaging magnification. Consequently, whenthe imaging magnification is increased, usability enabling fine-grainedoperation by the operator is demanded. In light of such circumstances,in the present embodiment, a robot arm apparatus enabling optimaloperation according to an image captured by an imaging unit is realized.

FIG. 1 will be referenced to describe an application example for thecase of a robot arm apparatus according to an embodiment of the presentdisclosure being used for medical use. FIG. 1 is an explanatory diagramfor describing an application example for the case of a robot armapparatus according to an embodiment of the present disclosure beingused for medical use.

FIG. 1 schematically illustrates an exemplary medical procedure usingthe robot arm apparatus according to the present embodiment.Specifically, FIG. 1 illustrates an example in which a doctor serving asa practitioner (user) 520 performs surgery on a medical procedure target(patient) 540 on a medical procedure table 530, for example, usingsurgical instruments 521 such as a scalpel, tweezers, and forceps. Inthe following description, the medical procedure refers to a generalconcept including various kinds of medical treatments that the doctorserving as the user 520 performs on the patient of the medical proceduretarget 540 such as surgery or an examination. The example of FIG. 1illustrates surgery as an example of the medical procedure, but themedical procedure using a robot arm apparatus 510 is not limited tosurgery and may be various kinds of other medical procedures such as anexamination using an endoscope.

The robot arm apparatus 510 according to the present embodiment isinstalled at the side of the medical procedure table 530. The robot armapparatus 510 includes a base unit 511 serving as a base and an arm unit512 extending from the base unit 511. The arm unit 512 includes aplurality of joint units 513 a, 513 b, 513 c, a plurality of links 514 aand 514 b connected by the joint units 513 a and 513b, and an imagingunit 515 installed at the front edge of the arm unit 512. In the exampleillustrated in FIG. 1, for the sake of simplification, the arm unit 512includes the 3 joint units 513 a to 513 c and the 2 links 514 a and 514b, but practically, for example, the number and the shape of the jointunits 513 a to 513 c and the links 514 a and 514 b and a direction ofthe driving shaft of the joint units 513 a to 513 c may be appropriatelyset to express a desired degree of freedom in view of a degree offreedom of the position and posture of the arm unit 512 and the imagingunit 515.

The joint units 513 a to 513 c have a function of connecting the links514 a and 514 b to be rotatable, and as the joint units 513 a to 513 care rotationally driven, driving of the arm unit 512 is controlled.Here, in the following description, the position of each component ofthe robot arm apparatus 510 is the position (coordinates) in a spacespecified for driving control, and the posture of each component is adirection (angle) to an arbitrary axis in a space specified for drivingcontrol. Further, in the following description, driving (or drivingcontrol) of the arm unit 512 refers to changing (controlling a changeof) the position and posture of each component of the arm unit 512 byperforming driving (or driving control) of the joint units 513 a to 513c and driving (or driving control) of the joint units 513 a to 513 c.

Various kinds of medical apparatuses are connected to the front edge ofthe arm unit 512 as the front edge unit. In the example illustrated inFIG. 1, the imaging unit 515 is installed at the front edge of the armunit 512 as an exemplary front edge unit. The imaging unit 515 is a unitthat acquires an image (a photographed image) of a photographing targetand is, for example, a camera capable of capturing a moving image or astill image. As illustrated in FIG. 1, the posture or the position ofthe arm unit 512 and the imaging unit 515 is controlled by the robot armapparatus 510 such that the imaging unit 515 installed at the front edgeof the arm unit 512 photographs a state of a medical procedure part ofthe medical procedure target 540. The front edge unit installed at thefront edge of the arm unit 512 is not limited to the imaging unit 515and may be various kinds of medical apparatuses. For example, themedical apparatus includes various kinds of units used when the medicalprocedure is performed such as an endoscope, a microscope, a unit havingan imaging function such as the imaging unit 515, various kinds ofmedical procedure instruments, and an examination apparatus. Asdescribed above, the robot arm apparatus 510 according to the presentembodiment is a medical robot arm apparatus equipped with a medicalapparatus. Further, a stereo camera having two imaging units (cameraunits) may be installed at the front edge of the arm unit 512, and mayperform photography so that an imaging target is displayed as a threedimensional (3D) image.

Further, a display device 550 such as a monitor or a display isinstalled at a position facing the user 520. The captured image of themedical procedure part captured by the imaging unit 515 is displayed ona display screen of the display device 550. The user 520 performsvarious kinds of treatments while viewing the captured image of themedical procedure part displayed on the display screen of the displaydevice 550.

As described above, in the present embodiment, in the medical field, atechnique of performing surgery while photographing the medicalprocedure part through the robot arm apparatus 510 is proposed. Here, invarious kinds of medical procedures including surgery, it is necessaryto reduce fatigue or a burden on the user 520 and the patient 540 byperforming the medical procedure efficiently. In order to satisfy such ademand, in the robot arm apparatus 510, for example, the followingcapabilities are considered desirable.

First, as a first point, the robot arm apparatus 510 should secure atask space for surgery. If the arm unit 512 or the imaging unit 515hinders a field of vision of the practitioner or impedes motion of ahand performing a treatment while the user 520 is performing variouskinds of treatments on the medical procedure target 540, the efficiencyof surgery is lowered. Further, in FIG. 1, although not illustrated, inan actual surgical scene, for example, a plurality of other doctorsand/or nurses performing various support tasks of handing an instrumentto the user 520 or checking various kinds of vital signs of the patient540 are commonly around the user 520 and the patient 540, and there areother devices for performing the support tasks, and thus a surgicalenvironment is complicated. Thus, a small size is desirable in the robotarm apparatus 510.

Next, as a second point, the robot arm apparatus 510 should have highoperability for moving the imaging unit 515. For example, the user 520may desire to observe the same medical procedure part at variouspositions and angles while performing a treatment on the medicalprocedure part according to a surgical part or surgical content. Inorder to change an angle at which the medical procedure part isobserved, it is necessary to change an angle of the imaging unit 515with respect to the medical procedure part, but at this time, it is moredesirable that only a photographing angle be changed in a state in whichthe photographing direction of the imaging unit 515 is fixed to themedical procedure part (that is, while photographing the same part).Thus, for example, the robot arm apparatus 510 should have operabilityof a high degree of freedom such as a turning movement (a pivotmovement) in which the imaging unit 515 moves within a surface of a conehaving the medical procedure part as an apex, and an axis of the cone isused as a pivot axis in the state in which the photographing directionof the imaging unit 515 is fixed to the medical procedure part. Sincethe photographing direction of the imaging unit 515 is fixed to acertain medical procedure part, the pivot movement is also called pointlock movement.

Further, in order to change the position and the angle of the imagingunit 515, for example, a method in which the user 520 manually moves thearm unit 512 to move the imaging unit 515 to a desired position and at adesired angle is considered. Thus, it is desirable that there beoperability enabling movement of the imaging unit 515, the pivotmovement, or the like to be easily performed even with one hand.

Further, there may be a demand from the user 520 to move a photographingcenter of a captured image captured by the imaging unit 515 from a parton which a treatment is being performed to another part (for example, apart on which a next treatment will be performed) while performing atreatment with both hands during surgery. Thus, various driving methodsof the arm unit 512 are necessary such as a method of controllingdriving of the arm unit 512 by an operation input from an input unitsuch as a pedal as well as a method of controlling driving of the armunit 512 by a manual motion when it is desired to change the positionand posture of the imaging unit 515.

As described above as the capability of the second point, the robot armapparatus 510 should have high operability enabling easy movement, forexample, by the pivot movement or the manual motion and satisfyingintuition or a desire of the user 520.

Lastly, as a third point, the robot arm apparatus 510 should havestability in the driving control of the arm unit 512. The stability inthe driving control of the arm unit 512 may be stability in the positionand posture of the front edge unit when the arm unit 512 is driven. Thestability in the driving control of the arm unit 512 also includessmooth movement and suppression of vibration (vibration suppression) ofthe front edge unit when the arm unit 512 is driven. For example, whenthe front edge unit is the imaging unit 515 as in the exampleillustrated in FIG. 1, if the position or the posture of the imagingunit 515 is unstable, the captured image displayed on the display screenof the display device 550 is unstable, and the user may have a feelingof discomfort. Particularly, when the robot arm apparatus 510 is usedfor surgery, a use method in which a stereo camera including two imagingunits (camera units) is installed as the front edge unit, and a 3D imagegenerated based on photographed images obtained by the stereo camera isdisplayed can be assumed. As described above, when the 3D image isdisplayed, if the position or the posture of the stereo camera isunstable, the user is likely to experience 3D sickness. Further, anobservation range photographed by the imaging unit 515 may be enlargedup to about φ15 mm depending on a surgical part or surgical content.When the imaging unit 515 enlarges and photographs a narrow range asdescribed above, slight vibration of the imaging unit 515 is shown as alarge shake or deviation of an imaged image. Thus, high positioningaccuracy with a permissible range of about 1 mm is necessary for drivingcontrol of the arm unit 512 and the imaging unit 515. As describedabove, high-accuracy responsiveness and high positioning accuracy arenecessary in driving control of the arm unit 512.

The inventors have reviewed existing general balance arms and robot armapparatuses based on position control in terms of the above-mentioned 3capabilities.

First, with regard to securing the task space for the surgery of thefirst point, in the general balance arm, a counter balance weight (alsocalled a counter weight or a balancer) for maintaining balance of forcewhen the arm unit is moved is installed inside the base unit or thelike, and thus it is difficult to reduce the size of the balance armapparatus, and it is difficult to say that the corresponding capabilityis fulfilled.

Further, with regard to the high operability of the second point, in thegeneral balance arm, only some driving of the arm unit, for example,only biaxial driving for moving the imaging unit on a (two-dimensional)plane is electric driving, and manual positioning is necessary formovement of the arm unit and the imaging unit, and thus it is difficultto say that high operability can be implemented. Further, in the generalrobot arm apparatus based on the position control, since it is difficultto flexibly deal with external force by the position control used fordriving control of the arm unit, that is, control of the position andposture of the imaging unit, the position control is commonly called“hard control” and is not suitable of implementing desired operabilitysatisfying the user's intuition.

Further, with regard to stability in driving control of the arm unit ofthe third point, the joint unit of the arm unit generally has factorsthat are not easily modelized such as friction, inertia, and the like.In the general balance arm or the robot arm apparatus based on theposition control, the factors serve as a disturbance in the drivingcontrol of the joint unit, and even when a theoretically appropriatecontrol value (for example, a current value applied to a motor of thejoint unit) is given, there are cases in which desired driving (forexample, rotation at a desired angle in the motor of the joint unit) isnot implemented, and it is difficult to implement high stabilitynecessary for driving control of the arm unit.

As described above, the inventors have reviewed robot arm apparatusesbeing used for medical purposes and learned that there is a demand forthe capabilities of the above-mentioned three points with regard to therobot arm apparatus. However, it is difficult for the general balancearm or the robot arm apparatus based on the position control to easilyfulfill such capabilities. The inventors have developed a robot armapparatus, a robot arm control system, a robot arm control method, and aprogram according to the present disclosure as a result of reviewingconfigurations satisfying the capabilities of the three points.Hereinafter, preferable embodiments of the configuration developed bythe inventors will be described in detail.

<2. Embodiment of Present Disclosure>

A robot arm control system according to an embodiment of the presentdisclosure will be described below. In the robot arm control systemaccording to the present embodiment, driving of a plurality of jointunits installed in the robot arm apparatus is controlled by whole bodycooperative control using generalized inverse dynamics. Further, idealjoint control of implementing an ideal response to a command value bycorrecting influence of a disturbance is applied to driving control ofthe joint unit.

In the following description of the present embodiment, an externalappearance of the robot arm apparatus according to the presentembodiment and a schematic configuration of the robot arm apparatus willbe first described in [2-1. External appearance of robot arm apparatus].Then, an overview of the generalized inverse dynamics and the idealjoint control used for control of the robot arm apparatus according tothe present embodiment will be described in [2-2. Generalized inversedynamics] and [2-3. Ideal joint control]. Then, a configuration of asystem for controlling the robot arm apparatus according to the presentembodiment will be described with reference to a functional blockdiagram in [2-4. Configuration of robot arm control system]. Lastly, aspecific example of the whole body cooperative control using thegeneralized inverse dynamics in the robot arm apparatus according to thepresent embodiment will be described in [2-5. Specific example ofpurpose of motion].

Further, the following description will proceed with an example in whicha front edge unit of an arm unit of a robot arm apparatus according toan embodiment of the present disclosure is an imaging unit, and amedical procedure part is photographed by the imaging unit duringsurgery as illustrated in FIG. 1 as an embodiment of the presentdisclosure, but the present embodiment is not limited to this example.The robot arm control system according to the present embodiment can beapplied even when a robot arm apparatus including a different front edgeunit is used for another purpose.

[2-1. External Appearance of Robot Arm Apparatus]

First, a schematic configuration of a robot arm apparatus according toan embodiment of the present disclosure will be described with referenceto FIG. 2. FIG. 2 is a schematic diagram illustrating an externalappearance of a robot arm apparatus according to an embodiment of thepresent disclosure.

Referring to FIG. 2, a robot arm apparatus 400 according to the presentembodiment includes a base unit 410 and an arm unit 420. The base unit410 serves as the base of the robot arm apparatus 400, and the arm unit420 extends from the base unit 410. Although not illustrated in FIG. 2,a control unit that controls the robot arm apparatus 400 in anintegrated manner may be installed in the base unit 410, and driving ofthe arm unit 420 may be controlled by the control unit. For example, thecontrol unit is configured with various kinds of signal processingcircuits such as a central processing unit (CPU) or a digital signalprocessor (DSP).

The arm unit 420 includes a plurality of joint units 421 a to 421 f, aplurality of links 422 a to 422 c that are connected with one another bythe joint units 421 a to 421 f, and an imaging unit 423 installed at thefront edge of the arm unit 420.

The links 422 a to 422 c are rod-like members, one end of the link 422 ais connected with the base unit 410 through the joint unit 421 a, theother end of the link 422 a is connected with one end of the link 422 bthrough the joint unit 421 b, and the other end of the link 422 b isconnected with one end of the link 422 c through the joint units 421 cand 421 d. Further, the imaging unit 423 is connected to the front edgeof the arm unit 420, that is, the other end of the link 422 c throughthe joint units 421 e and 421 f. As described above, the arm shapeextending from the base unit 410 is configured such that the base unit410 serves as a support point, and the ends of the plurality of links422 a to 422 c are connected with one another through the joint units421 a to 421 f.

The imaging unit 423 is a unit that acquires an image of a photographingtarget, and is, for example, a camera that captures a moving image, astill image. The driving of the arm unit 420 is controlled such that theposition and posture of the imaging unit 423 are controlled. In thepresent embodiment, for example, the imaging unit 423 photographs someregions of the body of the patient serving as the medical procedurepart. Here, the front edge unit installed at the front edge of the armunit 420 is not limited to the imaging unit 423, and various kinds ofmedical apparatuses may be connected to the front edge of the arm unit420 as the front edge unit. As described above, the robot arm apparatus400 according to the present embodiment is a medical robot arm apparatusequipped with a medical apparatus.

Here, the description of the robot arm apparatus 400 will proceed withcoordinate axes defined as illustrated in FIG. 2. Further, a verticaldirection, a longitudinal direction, and a horizontal direction aredefined according to the coordinate axes. In other words, a verticaldirection with respect to the base unit 410 installed on the floor isdefined as a z axis direction and a vertical direction. Further, adirection along which the arm unit 420 extends from the base unit 410 asa direction orthogonal to the z axis (that is, a direction in which theimaging unit 423 is positioned with respect to the base unit 410) isdefined as a y axis direction and a longitudinal direction. Furthermore,a direction that is orthogonal to the y axis and the z axis is an x axisdirection and a horizontal direction.

The joint units 421 a to 421 f connect the links 422 a to 422 c to berotatable. Each of the joint units 421 a to 421 f includes a rotationmechanism that includes an actuator and is rotationally driven on acertain rotary axis according to driving of the actuator. By controllingrotary driving in each of the joint units 421 a to 421 f, for example,it is possible to control driving of the arm unit 420 to extend orshorten (fold) the arm unit 420. Here, driving of the joint units 421 ato 421 f is controlled by the whole body cooperative control which willbe described in [2-2. Generalized inverse dynamics] and the ideal jointcontrol which will be described in [2-3. Ideal joint control]. Further,as described above, since the joint units 421 a to 421 f according tothe present embodiment include the rotation mechanism, in the followingdescription, driving control of the joint units 421 a to 421 fspecifically means controlling a rotational angle and/or generatedtorque (torque generated by the joint units 421 a to 421 f) of the jointunits 421 a to 421 f.

The robot arm apparatus 400 according to the present embodiment includesthe 6 joint units 421 a to 421 f, and implements 6 degrees of freedomwith regard to driving of the arm unit 420. Specifically, as illustratedin FIG. 2, the joint units 421 a, 421 d, and 421 f are installed suchthat the long axis directions of the links 422 a to 422 c connectedthereto and the photographing direction of the imaging unit 473connected thereto are set as the rotary axis direction, and the jointunits 421 b, 421 c, and 421 e are installed such that an x axisdirection serving as a direction in which connection angles of the links422 a to 422 c and the imaging unit 473 connected thereto are changedwithin a y-z plane (a plane specified by the y axis and the z axis) isset as the rotary axis direction. As described above, in the presentembodiment, the joint units 421 a, 421 d, and 421 f have a function ofperforming yawing, and the joint units 421 b, 421 c, and 421 e have afunction of performing pitching.

As the above-described configuration of the arm unit 420 is provided,the robot arm apparatus 400 according to the present embodiment canimplement the 6 degrees of freedom on driving of the arm unit 420, andthus can freely move the imaging unit 423 within a movable range of thearm unit 420. FIG. 2 illustrates a hemisphere as an exemplary movablerange of the imaging unit 423. When the central point of the hemisphereis the photographing center of the medical procedure part photographedby the imaging unit 423, the medical procedure part can be photographedat various angles by moving the imaging unit 423 on the sphericalsurface of the hemisphere in a state in which the photographing centerof the imaging unit 423 is fixed to the central point of the hemisphere.

A configuration of the joint units 421 a to 421 f illustrated in FIG. 2will be described herein in further detail with reference to FIG. 3.Further, a configuration of an actuator serving as a component mainlyrelated to the rotary driving of the joint units 421 a to 421 f amongthe components of the joint units 421 a to 421 f will be describedherein with reference to FIG. 3.

FIG. 3 is a cross-sectional diagram schematically illustrating a statein which an actuator of each of the joint units 421 a to 421 f accordingto an embodiment of the present disclosure is cut along a cross sectionpassing through the rotary axis. FIG. 3 illustrates an actuator amongthe components of the joint units 421 a to 421 f, but the joint units421 a to 421 f may have any other component. For example, the jointunits 421 a to 421 f have various kinds of components necessary fordriving of the arm unit 420 such as a control unit for controllingdriving of the actuator and a support member for connecting andsupporting the links 422 a to 422 c and the imaging unit 423 in additionto the components illustrated in FIG. 3. Further, in the abovedescription and the following description, driving of the joint unit ofthe arm unit may mean driving of the actuator in the joint unit.

As described above, in the present embodiment, driving of the jointunits 421 a to 421 f is controlled by the ideal joint control which willbe described later in [2-3. Ideal joint control]. Thus, the actuator ofthe joint units 421 a to 421 f illustrated in FIG. 3 is configured toperform driving corresponding to the ideal joint control. Specifically,the actuator of the joint units 421 a to 421 f is configured to be ableto adjust the rotational angles and torque associated with the rotarydriving in the joint units 421 a to 421 f Further, the actuator of thejoint units 421 a to 421 f is configured to be able to arbitrarilyadjust a viscous drag coefficient on a rotary motion. For example, it ispossible to implement a state in which rotation is easily performed(that is, the arm unit 420 is easily moved by a manual motion) by forceapplied from the outside or a state in which rotation is not easilyperformed (that is, the arm unit 420 is not easily moved by a manualmotion) by force applied from the outside.

Referring to FIG. 3, an actuator 430 of the joint units 421 a to 421 faccording to the present embodiment includes a motor 424, a motor driver425, a reduction gear 426, an encoder 427, a torque sensor 428, and adriving shaft 429. As illustrated in FIG. 3, the encoder 427, the motor424, the reduction gear 426, and the torque sensor 428 are connected tothe driving shaft 429 in series in the described order.

The motor 424 is a prime mover in the actuator 430, and causes thedriving shaft 429 to rotate about its axis. For example, the motor 424is an electric motor such as a brushless DC motor. In the presentembodiment, as the motor 424 is supplied with an electric current, therotary driving is controlled.

The motor driver 425 is a driver circuit (a driver integrated circuit(IC)) for supplying an electric current to the motor 424 androtationally driving the motor 424, and can control the number ofrevolutions of the motor 424 by adjusting an amount of electric currentsupplied to the motor 424. Further, the motor driver 425 can adjust theviscous drag coefficient on the rotary motion of the actuator 430 byadjusting an amount of electric current supplied to the motor 424.

The reduction gear 426 is connected to the driving shaft 429, andgenerates rotary driving force (that is, torque) having a certain valueby reducing the rotation speed of the driving shaft 429 generated by themotor 424 at a certain reduction ratio. A high-performance reductiongear of a backlashless type is used as the reduction gear 426. Forexample, the reduction gear 426 may be a Harmonic Drive (a registeredtrademark). The torque generated by the reduction gear 426 istransferred to an output member (not illustrated) (for example, aconnection member of the links 422 a to 422 c, the imaging unit 423, orthe like) at a subsequent stage through the torque sensor 428 connectedto an output shaft of the reduction gear 426.

The encoder 427 is connected to the driving shaft 429, and detects thenumber of revolutions of the driving shaft 429. It is possible to obtaininformation such as the rotational angle, the rotational angularvelocity, and the rotational angular acceleration of the joint units 421a to 421 f based on a relation between the number of revolutions of thedriving shaft 429 detected by the encoder and the reduction ratio of thereduction gear 426.

The torque sensor 428 is connected to the output shaft of the reductiongear 426, and detects the torque generated by the reduction gear 426,that is, the torque output by the actuator 430. In the followingdescription, the torque output by the actuator 430 is also referred tosimply as “generated torque.”

As described above, the actuator 430 can adjust the number ofrevolutions of the motor 424 by adjusting an amount of electric currentsupplied to the motor 424. Here, the reduction ratio of the reductiongear 426 may be appropriately set according to the purpose of the robotarm apparatus 400. Thus, the generated torque can be controlled byappropriately adjusting the number of revolutions of the motor 424according to the reduction ratio of the reduction gear 426. Further, inthe actuator 430, it is possible to obtain information such as therotational angle, the rotational angular velocity, and the rotationalangular acceleration of the joint units 421 a to 421 f based on thenumber of revolutions of the driving shaft 429 detected by the encoder427, and it is possible to detect the generated torque in the jointunits 421 a to 421 f through the torque sensor 428.

Further, the torque sensor 428 can detect external torque applied fromthe outside as well as the generated torque generated by the actuator430. Thus, as the motor driver 425 adjusts an amount of electric currentsupplied to the motor 424 based on the external torque detected by thetorque sensor 428, it is possible to adjust the viscous drag coefficienton the rotary motion and implement, for example, the state in whichrotation is easily or not easily performed by force applied from theoutside.

Here, a configuration of the torque sensor 428 will be described indetail with reference to FIGS. 4A and 4B. FIG. 4A is a schematic diagramschematically illustrating a state of the torque sensor 428 illustratedin FIG. 3 viewed in the axis direction of the driving shaft 429.

Referring to FIG. 4A, the torque sensor 428 includes an outer ringsection 431, an inner ring section 432, beam sections 433 a to 433 d,and distortion detecting elements 434 a to 434 d. As illustrated in FIG.4A, the outer ring section 431 and the inner ring section 432 areconcentrically arranged. In the present embodiment, the inner ringsection 432 is connected to an input side, that is, the output shaft ofthe reduction gear 426, and the outer ring section 431 is connected toan output side, that is, an output member (not illustrated) at asubsequent stage.

The 4 beam sections 433 a to 433 d are arranged between the outer ringsection 431 and the inner ring section 432 that are concentricallyarranged, and connect the outer ring section 431 with the inner ringsection 432. As illustrated in FIG. 4A, the beam sections 433 a to 433 dare interposed between the outer ring section 431 and the inner ringsection 432 so that two neighboring sections of the beam sections 433 ato 433 d form an angle of 90°.

The distortion detecting elements 434 a to 434 d are installed at thetwo sections facing each other, that is, disposed at an angle of 180°among the beam sections 433 a to 433 d. It is possible to detect thegenerated torque and the external torque of the actuator 430 based on adeformation amount of the beam sections 433 a to 433 d detected by thedistortion detecting elements 434 a to 434 d.

In the example illustrated in FIG. 4A, among the beam sections 433 a to433 d, the distortion detecting elements 434 a and 434 b are installedat the beam section 433 a, and the distortion detecting elements 434 cand 434 d are installed at the beam section 433 c. Further, thedistortion detecting elements 434 a and 434 b are installed with thebeam section 433 a interposed therebetween, and the distortion detectingelements 434 c and 434 d are installed with the beam section 433 cinterposed therebetween. For example, the distortion detecting elements434 a to 434 d are distortion gauges attached to the surfaces of thebeam sections 433 a and 433 c, and detect geometric deformation amountsof the beam sections 433 a and 433 c based on a change in electricalresistance. As illustrated in FIG. 4A, the distortion detecting elements434 a to 434 d are installed at 4 positions, and the detecting elements434 a to 434 d configure a so-called Wheatstone bridge. Thus, since itis possible to detect distortion using a so-called four-gauge technique,it is possible to reduce influence of interference of shafts other thana shaft in which distortion is detected, eccentricity of the drivingshaft 429, a temperature drift, or the like.

As described above, the beam sections 433 a to 433 d serve as adistortion inducing body whose distortion is detected. The type of thedistortion detecting elements 434 a to 434 d according to the presentembodiment is not limited to a distortion gauge, and any other elementmay be used. For example, the distortion detecting elements 434 a to 434d may be elements that detect the deformation amounts of the beamsections 433 a to 433 d based on a change in magnetic characteristics.

Although not illustrated in FIGS. 3 and 4A, the following configurationmay be applied in order to improve the detection accuracy of thegenerated torque and the external torque by the torque sensor 428. Forexample, when portions of the beam sections 433 a to 433 d which areconnected with the outer ring section 431 are formed at a thinnerthickness than other portions, since a support moment is released,linearity of a deformation amount to be detected is improved, andinfluence by a radial load is reduced. Further, when both the outer ringsection 431 and the inner ring section 432 are supported by a housingthrough a bearing, it is possible to exclude an action of other axialforce and a moment from both the input shaft and the output shaft.Further, in order to reduce another axial moment acting on the outerring section 431, a support bearing may be arranged at the other end ofthe actuator 430 illustrated in FIG. 3, that is, a portion at which theencoder 427 is arranged.

The configuration of the torque sensor 428 has been described above withreference to FIG. 4A. As described above, through the configuration ofthe torque sensor 428 illustrated in FIG. 4A, it is possible to detectthe generated torque and the external torque of the actuator 430 with ahigh degree of accuracy.

Here, in the present embodiment, the configuration of the torque sensor428 is not limited to the configuration illustrated in FIG. 4A and maybe any other configuration. Another exemplary configuration of thetorque sensor applied to the actuator 430 other than the torque sensor428 will be described with reference to FIG. 4B.

FIG. 4B is a schematic diagram illustrating another exemplaryconfiguration of the torque sensor applied to the actuator 430illustrated in FIG. 3. Referring to FIG. 4B, a torque sensor 428 aaccording to the present modified example includes an outer ring section441, an inner ring section 442, beam sections 443 a to 443 d, anddistortion detecting elements 444 a to 444 d. FIG. 4B schematicallyillustrates a state of the torque sensor 428 a viewed in the axisdirection of the driving shaft 429, similarly to FIG. 4A.

In the torque sensor 428 a, functions and configurations of the outerring section 441, the inner ring section 442, the beam sections 443 a to443 d, and the distortion detecting elements 444 a to 444 d are similarto the functions and the configurations of the outer ring section 431,the inner ring section 432, the beam sections 433 a to 433 d, and thedistortion detecting elements 434 a to 434 d of the torque sensor 428described above with reference to FIG. 4A. The torque sensor 428 aaccording to the present modified example differs in a configuration ofa connection portion of the beam sections 443 a to 443 d and the outerring section 441. Thus, the torque sensor 428 a illustrated in FIG. 4Bwill be described focusing on a configuration of the connection portionof the beam sections 443 a to 443 d and the outer ring section 441 thatis the difference with the torque sensor 428 illustrated in FIG. 4A, anda description of a duplicated configuration will be omitted.

Referring to FIG. 4B, the connection portion of the beam section 443 band the outer ring section 441 is enlarged and illustrated together witha general view of the torque sensor 428 a. In FIG. 4B, only theconnection portion of the beam section 443 b and the outer ring section441 which is one of the four connection portions of the beam sections443 a to 443 d and the outer ring section 441 is enlarged andillustrated, but the other 3 connection portions of the beam sections443 a, 443 c, and 443 d and the outer ring section 441 have the sameconfiguration.

Referring to an enlarged view in FIG. 4B, in the connection portion ofthe beam section 443 b and the outer ring section 441, an engagementconcave portion is formed in the outer ring section 441, and the beamsection 443 b is connected with the outer ring section 441 such that thefront edge of the beam section 443 b is engaged with the engagementconcave portion. Further, gaps G1 and G2 are formed between the beamsection 443 b and the outer ring section 441. The gap G1 indicates a gapbetween the beam section 443 b and the outer ring section 441 in adirection in which the beam section 443 b extends toward the outer ringsection 441, and the gap G2 indicates a gap between the beam section 443b and the outer ring section 441 in a direction orthogonal to thatdirection.

As described above, in the torque sensor 428 a, the beam sections 443 ato 443 d and the outer ring section 441 are arranged to be separatedfrom each other with the certain gaps G1 and G2. In other words, in thetorque sensor 428 a, the outer ring section 441 is separated from theinner ring section 442. Thus, since the inner ring section 442 has adegree of freedom of a motion without being bound to the outer ringsection 441, for example, even when vibration occurs at the time ofdriving of the actuator 430, a distortion by vibration can be absorbedby the air gaps G1 and G2 between the inner ring section 442 and theouter ring section 441. Thus, as the torque sensor 428 a is applied asthe torque sensor of the actuator 430, the generated torque and theexternal torque are detected with a high degree of accuracy.

For example, JP 2009-269102A and JP 2011-209099A which are patentapplications previously filed by the present applicant can be referredto for the configuration of the actuator 430 corresponding to the idealjoint control illustrated in FIGS. 3, 4A, and 4B.

The schematic configuration of the robot arm apparatus 400 according tothe present embodiment has been described above with reference to FIGS.2, 3, 4A, and 4B. Next, the whole body cooperative control and the idealjoint control for controlling driving of the arm unit 420, that is,driving of the joint units 421 a to 421 f in the robot arm apparatus 400according to the present embodiment, will be described.

[2-2. Generalized Inverse Dynamics]

Next, an overview of the generalized inverse dynamics used for the wholebody cooperative control of the robot arm apparatus 400 according to thepresent embodiment will be described.

The generalized inverse dynamics are basic operations in whole bodycooperative control of a multi-link structure of converting purposes ofmotion related to various dimensions in various kinds of operationspaces into torque to be generated by a plurality of joint units in viewof various kinds of constraint conditions in a multi-link structure (forexample, the arm unit 420 illustrated in FIG. 2 in the presentembodiment) configured such that a plurality of links are connected by aplurality of joint units.

The operation space is an important concept in the force control of therobot apparatus. The operation space is a space for describing arelation between force acting on the multi-link structure andacceleration of the multi-link structure. When the driving control ofthe multi-link structure is performed by the force control rather thanthe position control, the concept of the operation space is necessary inthe case in which a way of dealing with the multi-link structure and theenvironment is used as a constraint condition. The operation space is,for example, a space to which the multi-link structure belongs such as ajoint space, a Cartesian space, or a momentum space.

The purpose of motion indicates a target value in the driving control ofthe multi-link structure, and, for example, a target value of aposition, a speed, acceleration, force, or an impedance of themulti-link structure that is desired to be achieved through the drivingcontrol.

The constraint condition is a constraint condition related to, forexample, a position, a speed, acceleration, or force of the multi-linkstructure that is decided by the shape or the to structure of themulti-link structure, the environment around the multi-link structure, asetting performed by the user, or the like. For example, the constraintcondition includes information about generated force, a priority, thepresence or absence of a non-driven joint, vertical reactive force, afriction weight, a support polygon, and the like.

In the generalized inverse dynamics, in order to achieve both stabilityof numeric calculation and real-time processable operation efficiency,an operation algorithm is configured with a virtual force decisionprocess (a virtual force calculating process) serving as a first stageand an actual force conversion process (an actual force calculatingprocess) serving as a second stage. In the virtual force calculatingprocess serving as the first stage, virtual force serving as virtualforce that is necessary for achieving each purpose of motion and acts onthe operation space is decided in view of a priority of a purpose ofmotion and a maximum value of the virtual force. In the actual forcecalculating process serving as the second stage, the calculated virtualforce is converted into actual force that can be implemented by aconfiguration of an actual multi-link structure such as joint force orexternal force in view of a constraint related to a non-driven joint,vertical reactive force, a friction weight, a support polygon, or thelike. The virtual force calculating process and the actual forcecalculating process will be described below. In the followingdescription of the virtual force calculating process, the actual forcecalculating process, and the ideal joint control, for easierunderstanding, there are cases in which an exemplary configuration ofthe arm unit 420 of the robot arm apparatus 400 according to the presentembodiment illustrated in FIGS. 2 and 3 is described as a specificexample.

(2-2-1. Virtual Force Calculating Process)

A vector configured with certain physical quantities in the joint unitsof the multi-link structure is referred to as a “generalized variable q”(also referred to as a “joint value q” or a “joint space q”). Anoperation space x is defined by the following Equation (1) using a timedifferential value of the generalized variable q and a Jacobian J:

[Math 1]

{dot over (x)}=J{dot over (q)}  (1)

In the present embodiment, for example, q indicates a rotational anglein the joint units 421 a to 421 f of the arm unit 420. An equation ofmotion related to the operation space x is described by the followingEquation (2):

[Math 2]

{umlaut over (x)}=∧ ¹ f+c   (2)

Here, f indicates force acting on the operation space x. Further, ∧⁻¹indicates an operation space inertia inverse matrix, c indicatesoperation space bias acceleration, and ∧⁻¹ and c are expressed by thefollowing Equations (3) and (4).

[Math 3]

∧⁻¹ =JH ⁻¹ J ^(T)   (3)

c=JH ⁻¹(τ−b)+{dot over (J)}{dot over (q)}  (4)

H indicates a joint space inertia matrix, τ indicates joint force (forexample, generated torque in the joint units 421 a to 421 f)corresponding to the joint value q, and b is a term indicating gravity,Coriolis force, or centrifugal force.

In the generalized inverse dynamics, the purpose of motion of theposition and the speed related to the operation space x is known to beexpressed as acceleration of the operation space x. At this time, inorder to implement the operation space acceleration serving as thetarget value given as the purpose of motion from Equation (1), virtualforce f_(v) that has to act on the operation space x is obtained bysolving a sort of linear complementary problem (LCP) expressed by thefollowing Equation (5).

$\begin{matrix}\left\lbrack {{Math}\mspace{14mu} 4} \right\rbrack & \; \\{{{w + \overset{¨}{x}} = {{\Lambda^{- 1}f_{v}} + c}}{s.t.\mspace{14mu} \left\{ \begin{matrix}{\left( {\left( {w_{i} < 0} \right)\bigcap\left( {f_{v_{i}} = U_{i}} \right)} \right)\bigcup} \\{\left( {\left( {w_{i} > 0} \right)\bigcap\left( {f_{v_{i}} = L_{i}} \right)} \right)\bigcup} \\\left( {\left( {w_{i} = 0} \right)\bigcap\left( {L_{i} < f_{v_{i}} < U_{i}} \right)} \right)\end{matrix} \right.}} & (5)\end{matrix}$

Here, L_(i) and U_(i) are set to a negative lower limit value (including−∞) of an i-th component of f_(v) and a positive upper limit value(including +∞) of the i-th component of f_(v). The LCP can be solved,for example, using an iterative technique, a pivot technique, a methodusing robust acceleration control, or the like.

Further, the operation space inertia inverse matrix ∧⁻¹ and the biasacceleration c are large in a calculation cost when they are calculatedas in Equations (3) and (4) serving as definitional equations. Thus, amethod of performing the calculation process of the operation spaceinertia inverse matrix ∧⁻¹ at a high speed by applying a quasidynamicscalculation (FWD) of calculating generalized acceleration (jointacceleration) from generalized force (the joint force τ) of themulti-link structure has been proposed. Specifically, the operationspace inertia inverse matrix ∧⁻¹ and the bias acceleration c can beobtained based on information related to force acting on the multi-linkstructure (for example, the arm unit 420 and the joint units 421 a to421 f) such as the joint space q, the joint force τ, or the gravity gusing the forward dynamics calculation FWD. As described above, theoperation space inertia inverse matrix ∧⁻¹ can be calculated with acalculation amount of O(N) on the number N of joint units by applyingthe forward dynamics calculation FWD related to the operation space.

Here, as a setting example of the purpose of motion, a condition forachieving the target value (indicated by adding a bar above a secondorder differential of x) of the operation space acceleration by thevirtual force f_(vi) of an absolute value F_(i) or less can be expressedby the following Equation (6):

[Math 5]

L _(i) =−F _(i),

U_(i)=F_(i),

{umlaut over (x)}_(i)={umlaut over (x)} _(i)   (6)

As described above, the purpose of motion related to the position andthe speed of the operation space x can be represented as the targetvalue of the operation space acceleration and is specifically expressedby the following Equation (7) (the target value of the position and thespeed of the operation space x are indicated by adding a bar above x anda first order differential of x).

[Math 6]

{umlaut over (x)} _(i) =K _(p)( x _(i) −x _(i))+K _(v)( {dot over (x)}_(i) −{dot over (x)} _(i))   (7)

It is also possible to set the purpose of motion related to theoperation space (momentum, Cartesian relative coordinates, aninterlocked joint, and the like) represented by a linear sum of otheroperation spaces using an approach of a decomposition operation space.Further, it is necessary to give priorities to competing purposes ofmotion. The LCP is solved for each priority or in ascending order ofpriorities, and it is possible to cause virtual force obtained from aprevious LCP to act as known external force of a subsequent LCP.

(2-2-2. Actual Force Calculating Process)

In the actual force calculating process serving as the second stage ofthe generalized inverse dynamics, a process of replacing the virtualforce f_(v) obtained in (2-2-1. Virtual force decision process) withactual joint force and external force is performed. A condition ofimplementing generalized force τ_(v)=J_(v) ^(T)f_(v) based on virtualforce through generated torque τ_(a) generated by the joint unit andexternal force f_(e) is expressed by the following Equation (8).

$\begin{matrix}\left\lbrack {{Math}\mspace{14mu} 7} \right\rbrack & \; \\{{\begin{bmatrix}J_{vu}^{T} \\J_{va}^{T}\end{bmatrix}\left( {f_{v} - {\Delta \; f_{v}}} \right)} = {{\begin{bmatrix}J_{eu}^{T} \\J_{ea}^{T}\end{bmatrix}f_{e}} + \begin{bmatrix}0 \\\tau_{a}\end{bmatrix}}} & (8)\end{matrix}$

Here, a subscript a indicates a set of driven joint units (a drivenjoint set), and a subscript u indicates a set of non-driven joint units(a non-driven joint set). In other words, the upper portions in Equation(8) represent balance of force of a space (a non-driven joint space) bythe non-driven joint unit, and the lower portions represent balance offorce of a space (a driven joint space) by the driven joint unit. J_(vu)and J_(va) indicate a non-driven joint component and a driven jointcomponent of a Jacobian related to the operation space on which thevirtual force f_(v) acts, respectively. J_(eu) and J_(ea) indicate anon-driven joint component and a driven joint component of a Jacobianrelated to the operation space on which the external force f_(e) acts.Δf_(v) indicates a component of the virtual force f_(v) that is hardlyimplemented by actual force.

The upper portions in Equation (8) are undefined, and, for example,f_(e) and Δf_(v) can be obtained by solving a quadratic programmingproblem (QP) expressed by the following Equation (9).

$\begin{matrix}\left\lbrack {{Math}\mspace{14mu} 8} \right\rbrack & \; \\{{{\min \frac{1}{2}ɛ^{T}Q_{1}ɛ} + {\frac{1}{2}\xi^{T}Q_{2}\xi \mspace{14mu} {s.t.\mspace{11mu} U}\; \xi}} \geq v} & (9)\end{matrix}$

Here, ε is a difference between sides of the upper portions in Equation(8), and indicates an equation error. ξ is a connection vector of f_(e)and Δf_(v), and indicates a variable vector. Q₁ and Q₂ are positivedefinite symmetric matrices indicating weights at the time ofminimization. Further, an inequality constraint of Equation (9) is usedto express a constraint condition related to external force such asvertical reactive force, a friction cone, a maximum value of externalforce, and a support polygon. For example, an inequality constraintrelated to a rectangular support polygon is expressed by the followingEquation (10).

[Math 9]

|F _(x)|≤μ_(t)F_(z),

|F _(y)|≤μ_(t)F_(z),

F_(z)≥0,

|M _(x) |≤d _(y) F _(z),

|M _(y) |≤d _(x) F _(z),

|M _(z) |≤d _(r) F _(z),   (10)

Here, z indicates a normal direction of a contact surface, and x and yindicate two orthogonal tangential directions that are vertical to z.(F_(x),F_(y),F_(z)) and (M_(x),M_(y),M_(z)) are external force andexternal force moment acting on a contact point. μ_(t) and μ_(r)indicate friction coefficients related to translation and rotation.(d_(x),d_(y)) indicates a size of a support polygon.

The solutions f_(e) and Δf_(v) of a minimum norm or a minimum error areobtained from Equations (9) and (10). It is possible to obtain the jointforce τ_(a) necessary for implementing the purpose of motion bysubstituting f_(e) and Δf_(v) obtained from Equation (9) into the lowerportion of Equation (8).

In the case of a system in which the basis is fixed, and there is nonon-driven joint, all virtual force can be replaced only with jointforce, and f_(e)=0 and Δf_(v)=0 can be set in Equation (8). In thiscase, the following Equation (11) can be obtained for the joint forceτ_(a) from the lower portions in Equation (8).

[Math 10]

τ_(a)=J_(va) ^(T)f_(v)   (11)

The whole body cooperative control using the generalized inversedynamics according to the present embodiment has been described above.As described above, as the virtual force calculating process and theactual force calculating process are sequentially performed, it ispossible to obtain the joint force τ_(a) for achieving a desired purposeof motion. In other words, conversely, as the calculated joint forceτ_(a) is reflected in a theoretical model in motion of the joint units421 a to 421 f, the joint units 421 a to 421 f are driven to achieve adesired purpose of motion.

Further, for example, JP 2009-95959A and JP 2010-188471A which arepatent applications previously filed by the present applicant can bereferred to for the whole body cooperative control using the generalizedinverse dynamics described above, particularly, for the details of aprocess of deriving the virtual force f_(v), a method of solving the LCPand obtaining the virtual force f_(v), the resolution to the QP problem,and the like.

[2-3. Ideal Joint Control]

Next, the ideal joint control according to the present embodiment willbe described. Motion of each of the joint units 421 a to 421 f ismodelized by an equation of motion of a second order delay system of thefollowing Equation (12):

[Math 11]

I _(a) {umlaut over (q)}=τ _(a)+τ_(e) −v _(a) {dot over (q)}  (12)

Here, I_(a) indicates an inertia moment (inertia) in a joint unit, τ_(a)indicates generated torque of the joint units 421 a to 421 f, τ _(e)indicates external torque acting on each of the joint units 421 a to 421f, and v_(e) indicates a viscous drag coefficient in each of the jointunits 421 a to 421 f Equation (12) can also be regarded as a theoreticalmodel representing motion of the actuator 430 in the joint units 421 ato 421 f.

As described above in [2-2. Generalized inverse dynamics], through thecalculation using the generalized inverse dynamics, it is possible tocalculate τ_(a) serving as actual force that each of the joint units 421a to 421 f has to use to implement the purpose of motion using thepurpose of motion and the constraint condition. Thus, ideally, aresponse according to the theoretical model expressed by Equation (12)is implemented, that is, a desired purpose of motion is achieved byapplying each calculated τ_(a) to Equation (12).

However, practically, there are cases in which an error (a modelizationerror) between motion of the joint units 421 a to 421 f and thetheoretical model expressed by Equation (12) occurs due to influence ofvarious disturbances. The modelization error is classified into an errorcaused by a mass property such as a weight, a center of gravity, or atensor of inertia of the multi-link structure and an error caused byfriction, inertia, or the like in the joint units 421 a to 421 f. Ofthese, the modelization error of the former caused by the mass propertycan be relatively easily reduced at the time of construction of thetheoretical model by applying high-accuracy computer aided design (CAD)data or an identification method.

Meanwhile, the modelization error of the latter caused by friction,inertia, or the like in the joint units 421 a to 421 f occurs due to aphenomenon that it is difficult to modelize, for example, friction orthe like in the reduction gear 426 of the joint units 421 a to 421 f,and an unignorable modelization error may remain at the time ofconstruction of the theoretical model. Further, there is likely to be anerror between a value of an inertia I_(a) or a viscous drag coefficientv_(e) in Equation (12) and an actual value in the joint units 421 a to421 f. The error that is hardly modelized may act as a disturbance inthe driving control of the joint units 421 a to 421 f. Thus, due toinfluence of such a disturbance, practically, there are cases in whichmotion of the joint units 421 a to 421 f does not respond as in thetheoretical model expressed by Equation (12). Thus, there are cases inwhich it is difficult to achieve the purpose of motion of the controltarget even when the actual force τ_(a) serving as the joint forcecalculated by the generalized inverse dynamics is applied. In thepresent embodiment, an active control system is added to each of thejoint units 421 a to 421 f, and thus the response of the joint units 421a to 421 f is considered to be corrected such that an ideal responseaccording to the theoretical model expressed by Equation (12) isperformed. Specifically, in the present embodiment, torque control of afriction compensation type using the torque sensors 428 and 428 a of thejoint units 421 a to 421 f is performed, and in addition, it is possibleto perform an ideal response according to an ideal value even on theinertia I_(a) and the viscous drag coefficient v_(a) for the requestedgenerated torque τ_(a) and the requested external torque τ_(e).

In the present embodiment, controlling driving of the joint unit suchthat the joint units 421 a to 421 f of the robot arm apparatus 400perform the ideal response expressed by Equation (12) is referred to asthe ideal joint control as described above. Here, in the followingdescription, an actuator whose driving is controlled by the ideal jointcontrol is also referred to as a “virtualized actuator (VA)” since theideal response is performed. The ideal joint control according to thepresent embodiment will be described below with reference to FIG. 5.

FIG. 5 is an explanatory diagram for describing the ideal joint controlaccording to an embodiment of the present disclosure. FIG. 5schematically illustrates a conceptual computing unit that performsvarious kinds of operations according to the ideal joint control usingblocks.

Referring to FIG. 5, an actuator 610 schematically illustrates amechanism of the actuator 430 illustrated in FIG. 3, and a motor 611, areduction gear 612, an encoder 613, and a torque sensor 614 correspondto the motor 424, the reduction gear 426, the encoder 427, and thetorque sensor 428 (or the torque sensor 428 a illustrated in FIG. 4B)which are illustrated in FIG. 3.

Here, when the actuator 610 performs the response according to thetheoretical model expressed by Equation (12), it means that therotational angular acceleration at the left side is achieved when theright side of Equation (12) is given. Further, as expressed in Equation(12), the theoretical model includes an external torque term τ_(e)acting on the actuator 610. In the present embodiment, in order toperform the ideal joint control, the external torque τ_(e) is measuredby the torque sensor 614. Further, a disturbance observer 620 is appliedto calculate a disturbance estimation value τ_(d) serving as anestimation value of torque caused by a disturbance based on a rotationalangle q of the actuator 610 measured by the encoder 613.

A block 631 represents a computing unit that performs an operationaccording to the ideal joint model of the joint units 421 a to 421 fexpressed by Equation (12). The block 631 can receive the generatedtorque τ_(a), the external torque τ_(e), and the rotational angularvelocity (the first order differential of the rotational angle q) andoutput the rotational angular acceleration target value (a second orderdifferential of a rotational angle target value q^(ref)) shown at theleft side of Equation (12).

In the present embodiment, the generated torque τ_(a) calculated by themethod described in [2-2. Generalized inverse dynamics] and the externaltorque τ_(e) measured by the torque sensor 614 are input to the block631. Meanwhile, the rotational angle q measured by the encoder 613 isinput to a block 632 indicating a computing unit that performsdifferential operation, and thus the rotational angular velocity (thefirst order differential of the rotational angle q) is calculated. Inaddition to the generated torque τ_(a) and the external torque τ_(e),the rotational angular velocity calculated by the block 632 is input tothe block 631, and thus the rotational angular acceleration target valueis calculated by the block 631. The calculated rotational angularacceleration target value is input to a block 633.

The block 633 indicates a computing unit that calculates torque to begenerated in the actuator 610 based on the rotational angularacceleration of the actuator 610. In the present embodiment,specifically, the block 633 can obtain a torque target value τ^(ref) bymultiplying a nominal inertia J_(n) of the actuator 610 to therotational angular acceleration target value. In the ideal response, adesired purpose of motion is achieved by causing the actuator 610 togenerate the torque target value τ^(ref), but there are cases in whichan actual response is influenced by a disturbance or the like asdescribed above. Thus, in the present embodiment, the disturbanceestimation value τ_(d) is calculated by the disturbance observer 620,and the torque target value τ^(ref) is corrected using the disturbanceestimation value τ_(d).

A configuration of the disturbance observer 620 will be described. Asillustrated in FIG. 5, the disturbance observer 620 calculates thedisturbance estimation value τ_(d) based on a torque command value τ andthe rotational angular velocity calculated from the rotational angle qmeasured by the encoder 613. Here, the torque command value τ is atorque value to be finally generated by the actuator 610 after influenceof the disturbance is corrected. For example, when no disturbanceestimation value τ_(d) is calculated, the torque command value τ is usedas the torque target value τ^(ref).

The disturbance observer 620 is configured with a block 634 and a block635. The block 634 is a computing unit that calculates torque to begenerated by the actuator 610 based on the rotational angular velocityof the actuator 610. In the present embodiment, specifically, therotational angular velocity calculated by the block 632 based on therotational angle q measured by the encoder 613 is input to the block634. The block 634 can obtain the rotational angular acceleration byperforming an operation expressed by a transfer function J_(n)s, thatis, by differentiating the rotational angular velocity, and calculate anestimation value (a torque estimation value) of torque actually actingon the actuator 610 by multiplying the calculated rotational angularacceleration by the nominal inertia J_(n).

In the disturbance observer 620, a difference between the torqueestimation value and the torque command value τ is obtained, and thusthe disturbance estimation value τ_(d) serving as a value of torque by adisturbance is estimated. Specifically, the disturbance estimation valueτ_(d) may be a difference between the torque command value τ in theprevious control and the torque estimation value in the current control.Since the torque estimation value calculated by the block 634 is basedon an actual measurement value, and the torque command value τcalculated by the block 633 is based on the ideal theoretical model ofthe joint units 421 a to 421 f indicated by the block 631, it ispossible to estimate influence of a disturbance that is not consideredin the theoretical model by obtaining the difference of the two values.

The disturbance observer 620 is further provided with a low pass filter(LPF) indicated by the block 635 in order to prevent a divergence of asystem. The block 635 performs an operation represented by a transferfunction g/(s+g), outputs only a low frequency component in response toan input value, and stabilizes a system. In the present embodiment, adifference value between the torque estimation value calculated by theblock 634 and the torque command value τ^(ref) is input to the block635, and the low frequency component is calculated as the disturbanceestimation value τ_(d).

In the present embodiment, feedforward control of adding the disturbanceestimation value τ_(d) calculated by the disturbance observer 620 to thetorque target value τ^(ref) is performed, and thus the torque commandvalue τ serving as a torque value to be finally generated by theactuator 610 is calculated. Then, the actuator 610 is driven based onthe torque command value τ. Specifically, the torque command value τ isconverted into a corresponding electric current value (an electriccurrent command value), the electric current command value is applied tothe motor 611, so that the actuator 610 is driven.

By employing the configuration described above with reference to FIG. 5,in the driving control of the joint units 421 a to 421 f according tothe present embodiment, even when there is a disturbance component suchas friction, it is possible for the response of the actuator 610 tofollow the target value. Further, it is possible to perform the idealresponse according to the inertia I_(a) and the viscous drag coefficientv_(a) assumed by the theoretical model in the driving control of thejoint units 421 a to 421 f.

For example, JP 2009-269102A that is a patent application previouslyfiled by the present applicant can be referred to for the details of theabove-described ideal joint control.

The ideal joint control according to the present embodiment has beendescribed above with reference to FIG. 5 together with the generalizedinverse dynamics used in the present embodiment. As described above, inthe present embodiment, the whole body cooperative control ofcalculating driving parameters (for example, the generated torque valuesof the joint units 421 a to 421 f) of the joint units 421 a to 421 f forachieving the purpose of motion of the arm unit 420 is performed in viewof the constraint condition using the generalized inverse dynamics.Further, as described above with reference to FIG. 5, in the presentembodiment, as correction in which influence of a disturbance isconsidered is performed on the generated torque value calculated by thewhole body cooperative control using the generalized inverse dynamics,the ideal joint control of implementing the ideal response based on thetheoretical model in the driving control of the joint units 421 a to 421f is performed. Thus, in the present embodiment, it is possible toperform high-accuracy driving control for achieving the purpose ofmotion for driving of the arm unit 420.

[2-4. Configuration of Robot Arm Control System]

Next, a configuration of the robot arm control system according to thepresent embodiment in which the whole body cooperative control and theideal joint control described in [2-2. Generalized inverse dynamics] and[2-3. Ideal joint control] are applied to the driving control of therobot arm apparatus will be described.

An exemplary configuration of the robot arm control system according toan embodiment of the present disclosure will be described with referenceto FIG. 6. FIG. 6 is a functional block diagram illustrating anexemplary configuration of the robot arm control system according to anembodiment of the present disclosure. In the robot arm control systemillustrated in FIG. 6, components related to driving control of the armunit of the robot arm apparatus are mainly illustrated.

Referring to FIG. 6, a robot arm control system 1 according to anembodiment of the present disclosure includes a robot arm apparatus 10,a control device 20, and a display device 30. In the present embodiment,various kinds of operations in the whole body cooperative controldescribed in [2-2. Generalized inverse dynamics] and the ideal jointcontrol described in [2-3. Ideal joint control] through the controldevice 20 are performed, and driving of the arm unit of the robot armapparatus 10 is controlled based on the operation result. Further, thearm unit of the robot arm apparatus 10 is provided with an imaging unit140 which will be described later, and an image captured by the imagingunit 140 is displayed on a display screen of the display device 30.Next, configurations of the robot arm apparatus 10, the control device20, and the display device 30 will be described in detail. Note that inthis specification, a system including a robot arm apparatus 10 and acontrol device 20 is designated simply a robot arm apparatus in somecases.

The robot arm apparatus 10 includes an arm unit having a multi-linkstructure configured with a plurality of joint units and a plurality oflinks, and drives the arm unit in the movable range to control theposition and posture of the front edge unit installed at the front edgeof the arm unit. The robot arm apparatus 10 corresponds to the robot armapparatus 400 illustrated in FIG. 2.

Referring to FIG. 6, the robot arm apparatus 10 includes an arm controlunit 110 and an arm unit 120. The arm unit 120 includes a joint unit 130and the imaging unit 140.

The arm control unit 110 controls the robot arm apparatus 10 in anintegrated manner, and controls driving of the arm unit 120. The armcontrol unit 110 corresponds to the control unit (not illustrated inFIG. 2) described above with reference to FIG. 2. Specifically, the armcontrol unit 110 includes a drive control unit 111, and controls drivingof the arm unit 120, and driving of the arm unit 120 is controlled bycontrolling driving of the joint unit 130 according to control of thedrive control unit 111. More specifically, the drive control unit 111controls the number of revolutions of the motor in the actuator of thejoint unit 130 and the rotational angle and the generated torque of thejoint unit 130 by controlling an amount of electric current supplied tothe motor. Here, as described above, driving control of the arm unit 120by the drive control unit 111 is performed based on the operation resultin the control device 20. Thus, an amount of electric current that iscontrolled by the drive control unit 111 and supplied to the motor inthe actuator of the joint unit 130 is an amount of electric currentdecided based on the operation result in the control device 20.

The arm unit 120 has a multi-link structure configured with a pluralityof joint units and a plurality of links, and driving of the arm unit 120is controlled according to control of the arm control unit 110. The armunit 120 corresponds to the arm unit 420 illustrated in FIG. 2. The armunit 120 includes the joint unit 130 and the imaging unit 140. Further,since the plurality of joint units of the arm unit 120 have the samefunction and configuration, a configuration of one joint unit 130representing the plurality of joint units is illustrated in FIG. 6.

The joint unit 130 connects links to be rotatable in the arm unit 120,and the rotary driving of the joint unit 130 is controlled according tocontrol of the arm control unit 110 such that the arm unit 120 isdriven. The joint unit 130 corresponds to the joint units 421 a to 421 fillustrated in FIG. 2. Further, the joint unit 130 includes an actuator,and the actuator has a configuration similar to, for example, theconfiguration illustrated in FIGS. 3, 4A, and 4B.

The joint unit 130 includes a joint driving unit 131 and a joint statedetecting unit 132.

The joint driving unit 131 is a driving mechanism in the actuator of thejoint unit 130, and as the joint driving unit 131 is driven, the jointunit 130 is rotationally driven. The drive control unit 111 controlsdriving of the joint driving unit 131. For example, the joint drivingunit 131 is a component corresponding to the motor 424 and the motordriver 425 illustrated in FIG. 3, and driving the joint driving unit 131corresponds to the motor driver 425 driving the motor 424 with an amountof electric current according to a command given from the drive controlunit 111.

The joint state detecting unit 132 detects the state of the joint unit130. Here, the state of the joint unit 130 may mean a motion state ofthe joint unit 130. For example, the state of the joint unit 130includes information such as the rotational angle, the rotationalangular velocity, the rotational angular acceleration, and the generatedtorque of the joint unit 130. In the present embodiment, the joint statedetecting unit 132 includes a rotational angle detecting unit 133 thatdetects the rotational angle of the joint unit 130 and a torquedetecting unit 134 that detects the generated torque and the externaltorque of the joint unit 130. The rotational angle detecting unit 133and the torque detecting unit 134 correspond to the encoder 427 of theactuator 430 illustrated in FIG. 3 and the torque sensors 428 and 428 aillustrated in FIGS. 4A and 4B. The joint state detecting unit 132transmits the detected state of the joint unit 130 to the control device20.

The imaging unit 140 is an example of the front edge unit installed atthe front edge of the arm unit 120, and acquires an image of aphotographing target. The imaging unit 140 corresponds to the imagingunit 423 illustrated in FIG. 2. Specifically, the imaging unit 140 is,for example, a camera capable of photographing a photographing target ina moving image format or a still image format. More specifically, theimaging unit 140 includes a plurality of light receiving elementsarranged two dimensionally, and can perform photoelectric conversion inthe light receiving elements and acquire an image signal indicating animage of a photographing target. The imaging unit 140 transmits theacquired image signal to the display device 30.

Further, similarly to the robot arm apparatus 400 of FIG. 2 in which theimaging unit 423 is installed at the front edge of the arm unit 420, inthe robot arm apparatus 10, the imaging unit 140 is actually installedat the front edge of the arm unit 120. In FIG. 6, the form in which theimaging unit 140 is installed at the front edge of the last link throughthe plurality of joint units 130 and a plurality of links is representedby schematically illustrating the link between the joint unit 130 andthe imaging unit 140.

Further, in the present embodiment, various kinds of medical apparatusesmay be connected to the front edge of the arm unit 120 as the front edgeunit. As the medical apparatus, for example, there are various kinds ofunits used when the medical procedure is performed such as various kindsof medical procedure instruments including a scalpel or forceps or oneunit of various kinds of examination apparatuses including a probe of anultrasonic examination apparatus. Further, in the present embodiment,the imaging unit 140 illustrated in FIG. 6 or a unit having an imagingfunction such as an endoscope or a microscope may also be included as amedical apparatus. As described above, the robot arm apparatus 10according to the present embodiment may be a medical robot arm apparatusincluding a medical apparatus. Similarly, the robot arm control system 1according to the present embodiment may be a medical robot arm controlsystem. Further, a stereo camera including two imaging units (cameraunits) may be installed at the front edge of the arm unit 120, andphotography may be performed so that an imaging target is displayed as a3D image.

The function and configuration of the robot arm apparatus 10 have beendescribed above. Next, a function and configuration of the controldevice 20 will be described. Referring to FIG. 6, the control device 20includes an input unit 210, a storage unit 220, and a control unit 230.

The control unit 230 controls the control device 20 in an integratedmanner, and performs various kinds of operations for controlling drivingof the arm unit 120 in the robot arm apparatus 10. Specifically, inorder to control driving of the arm unit 120 of the robot arm apparatus10, the control unit 230 performs various kinds of operations in thewhole body cooperative control and the ideal joint control. The functionand configuration of the control unit 230 will be described below indetail, but the whole body cooperative control and the ideal jointcontrol have already been described in [2-2. Generalized inversedynamics] and [2-3. Ideal joint control], and thus a description thereofwill be omitted here.

The control unit 230 includes a whole body cooperative control unit 240,and an ideal joint control unit 250.

The whole body cooperative control unit 240 performs various kinds ofoperations related to the whole body cooperative control using thegeneralized inverse dynamics. In the present embodiment, the whole bodycooperative control unit 240 acquires a state (an arm state) of the armunit 120 based on the state of the joint unit 130 detected by the jointstate detecting unit 132. Further, the whole body cooperative controlunit 240 calculates a control value for the whole body cooperativecontrol of the arm unit 120 in the operation space based on the armstate and the purpose of motion and the constraint condition of the armunit 120 using the generalized inverse dynamics. For example, theoperation space refers to a space for describing a relation betweenforce acting on the arm unit 120 and acceleration generated in the armunit 120.

The whole body cooperative control unit 240 includes an arm stateacquiring unit 241, an operation condition setting unit 242, a virtualforce calculating unit 243, and an actual force calculating unit 244.

The arm state acquiring unit 241 acquires the state (the arm state) ofthe arm unit 120 based on the state of the joint unit 130 detected bythe joint state detecting unit 132. Here, the arm state may mean themotion state of the arm unit 120. For example, the arm state includesinformation such as a position, a speed, acceleration, or force of thearm unit 120. As described above, the joint state detecting unit 132acquires information such as the rotational angle, the rotationalangular velocity, the rotational angular acceleration, or the generatedtorque of each of the joint units 130 as the state of the joint unit130. Further, as will be described later, the storage unit 220 storesvarious kinds of information that is processed by the control device 20,and in the present embodiment, the storage unit 220 may store variouskinds of information (arm information) related to the arm unit 120, forexample, the number of joint units 130 and the number of linksconfiguring the arm unit 120, a connection state of the link and thejoint unit 130, and the length of the link. The arm state acquiring unit241 can acquire the corresponding information from the storage unit 220.Thus, the arm state acquiring unit 241 can acquire information such asthe positions (coordinates) of the plurality of joint units 130, aplurality of links, and the imaging unit 140 on the space (that is, theshape of the arm unit 120 or the position and posture of the imagingunit 140) or force acting on each of the joint units 130, the link, andthe imaging unit 140 based on the state of the joint unit 130 and thearm information. The arm state acquiring unit 241 transmits the acquiredarm information to the operation condition setting unit 242.

The operation condition setting unit 242 sets an operation condition inan operation related to the whole body cooperative control using thegeneralized inverse dynamics. Here, the operation condition may be thepurpose of motion and the constraint condition. The purpose of motionmay be various kinds of information related to a motion of the arm unit120. Specifically, the purpose of motion may be a target value of theposition and posture (coordinates), a speed, acceleration, and force ofthe imaging unit 140 or a target value of the position (coordinates), aspeed, acceleration, and force of the plurality of joint units 130 and aplurality of links of the arm unit 120. The constraint condition may bevarious kinds of information for constricting the motion of the arm unit120. Specifically, the constraint condition may be coordinates of aregion into which none of the components of the arm unit should move,values of a speed and acceleration at which the arm unit should notmove, a value of force that should not be generated, or the like.Further, a constraint range of various kinds of physical quantities inthe constraint condition may be set from ones that are difficult for thearm unit 120 to implement structurally or may be appropriately set bythe user. Further, the operation condition setting unit 242 includes aphysical model (for example, one in which the number of linksconfiguring the arm unit 120, the length of the link, the connectionstate of the link through the joint unit 130, the movable range of thejoint unit 130, and the like are modelized) for the structure of the armunit 120, and may set the motion condition and the constraint conditionby generating a control model in which a desired motion condition and adesired constraint condition are reflected in the physical model.

In the present embodiment, it is possible to appropriately set thepurpose of motion and the constraint condition and cause the arm unit120 to perform a desired movement. For example, it is possible to setthe target value of the position of the imaging unit 140 as the purposeof motion and move the imaging unit 140 to the target position, and itis also possible to set a movement constraint according to theconstraint condition, for example, to prevent the arm unit 120 frominvading a certain region in a space and then drive the arm unit 120.

As a specific example of the purpose of motion, for example, the purposeof motion may be a pivot movement serving as a turning movement in whichthe imaging unit 140 moves within a plane of a cone having a medicalprocedure part as an apex, and an axis of the cone is used as a pivotaxis in a state in which the photographing direction of the imaging unit140 is fixed to the medical procedure part. In the pivot movement, theturning movement may be performed in a state in which a distance betweenthe imaging unit 140 and a point corresponding to the apex of the coneis maintained constant. As the pivot movement is performed, it ispossible to observe an observation part at an equal distance and atdifferent angles, and thus it is possible to improve a convenience ofthe user performing surgery.

Another specific example, the purpose of motion may be contentcontrolling the generated torque in each of the joint units 130.Specifically, the purpose of motion may be a power assist movement ofcontrolling the state of the joint unit 130 such that gravity acting onthe arm unit 120 is negated and controlling the state of the joint unit130 such that movement of the arm unit 120 is supported in a directionof force given from the outside. More specifically, in the power assistmovement, driving of each of the joint units 130 is controlled such thateach of the joint units 130 generates the generated torque for negatingexternal torque by gravity in each of the joint units 130 of the armunit 120, and thus the position and posture of the arm unit 120 are heldin a certain state. When external torque is further applied from theoutside (for example, from the user) in this state, driving of each ofthe joint units 130 is controlled such that each of the joint units 1generates the generated torque in the same direction as the appliedexternal torque. As the power assist movement is performed, when theuser manually moves the arm unit 120, the user can move the arm unit 120by small force, and thus a feeling of moving the arm unit 120 in anon-gravity state can be given to the user. Further, it is possible tocombine the pivot movement with the power assist movement.

Here, in the present embodiment, the purpose of motion may mean amovement (motion) of the arm unit 120 implemented in the whole bodycooperative control or may mean an instantaneous purpose of motion (thatis, the target value in the purpose of motion) in the correspondingmovement. For example, in the case of the pivot movement, performing thepivot movement by the imaging unit 140 is the purpose of motion, but,for example, a value of the position or the speed of the imaging unit140 in the cone plane in the pivot movement is set as an instantaneouspurpose of motion (the target value in the purpose of motion) while thepivot movement is being performed. Further, for example, in the case ofthe power assist movement, performing the power assist movement forsupporting movement of the arm unit 120 in the direction of forceapplied from the outside is the purpose of motion, but a value of thegenerated torque in the same direction as the external torque applied toeach of the joint units 130 is set as an instantaneous purpose of motion(the target value in the purpose of motion) while the power assistmovement is being performed.

In the present embodiment, the purpose of motion is a concept includingboth the instantaneous purpose of motion (for example, the target valueof the position, the speed, or force of each component of the arm unit120 during a certain period of time) and movement of each component ofthe arm unit 120 implemented over time as a result of continuouslyachieving the instantaneous purpose of motion. In each step in anoperation for the whole body cooperative control in the whole bodycooperative control unit 240, the instantaneous purpose of motion is seteach time, and the operation is repeatedly performed, so that a desiredpurpose of motion is finally achieved.

Further, in the present embodiment, when the purpose of motion is set,the viscous drag coefficient in the rotary motion of each of the jointunits 130 may be appropriately set as well. As described above, thejoint unit 130 according to the present embodiment is configured to beable to appropriately adjust the viscous drag coefficient in the rotarymotion of the actuator 430. Thus, as the viscous drag coefficient in therotary motion of each of the joint units 130 is also set at the time ofsetting of the purpose of motion, for example, it is possible toimplement the state in which rotation is easily or not easily performedby force applied from the outside. For example, in the case of the powerassist movement, as the viscous drag coefficient in the joint unit 130is set to be small, the user can move the arm unit 120 by small force,and the user can have a non-gravity feeling. As described above, theviscous drag coefficient in the rotary motion of each of the joint units130 may be appropriately set according to content of the purpose ofmotion.

The specific examples of the purpose of motion will be described againin detail in [2-5. Specific example of purpose of motion].

Here, in the present embodiment, as will be described later, the storageunit 220 may store a parameter related to the operation condition suchas the purpose of motion or the constraint condition used in anoperation related to the whole body cooperative control. The operationcondition setting unit 242 can set the constraint condition stored inthe storage unit 220 as the constraint condition used in the operationof the whole body cooperative control.

Further, in the present embodiment, the operation condition setting unit242 can set the purpose of motion by a plurality of methods. Forexample, the operation condition setting unit 242 may set the purpose ofmotion based on the arm state transmitted from the arm state acquiringunit 241. As described above, the arm state includes information of theposition of the arm unit 120 and information of force acting on the armunit 120. Thus, for example, when the user manually moves the arm unit120, information related to how the user moves the arm unit 120 is alsoacquired as the arm state through the arm state acquiring unit 241.Thus, the operation condition setting unit 242 can set, for example, theposition to which the user has moved the arm unit 120, a speed at whichthe user has moved the arm unit 120, or force by which the user hasmoved the arm unit 120 as the instantaneous purpose of motion based onthe acquired arm state. As the purpose of motion is set as describedabove, control is performed such that driving of the arm unit 120follows and supports movement of the arm unit 120 by the user.

Further, for example, the operation condition setting unit 242 may setthe purpose of motion based on an instruction input from the input unit210 by the user. As will be described later, the input unit 210 is aninput interface through which the user inputs, for example, informationor a command related to driving control of the robot arm apparatus 10 tothe control device 20, and in the present embodiment, the purpose ofmotion may be set based on an operation input from the input unit 210 bythe user. Specifically, the input unit 210 includes an operation unitoperated by the user such as a lever or a pedal, and, for example, theoperation condition setting unit 242 may set the position or the speedof each component of the arm unit 120 as the instantaneous purpose ofmotion according to an operation of the lever, the pedal, or the like.

Further, for example, the operation condition setting unit 242 may setthe purpose of motion stored in the storage unit 220 as the purpose ofmotion used in the operation of the whole body cooperative control. Forexample, in the case of the purpose of motion for causing the imagingunit 140 to stop at a certain point in the space, coordinates of thecertain point can be set as the purpose of motion in advance. Further,for example, in the case of the purpose of motion for causing theimaging unit 140 to move along a certain trajectory in the space,coordinates of points indicating the certain trajectory can be set asthe purpose of motion in advance. As described above, when the purposeof motion can be set in advance, the purpose of motion may be stored inthe storage unit 220 in advance. Further, for example, in the case ofthe pivot movement, the purpose of motion is limited to setting aposition, a speed, or the like in the plane of the cone as the targetvalue, and in the case of the power assist movement, the purpose ofmotion is limited to setting force as the target value. As describedabove, when the purpose of motion such as the pivot movement or thepower assist movement is set in advance, for example, informationrelated to a range or a type of the target value that can be set as theinstantaneous purpose of motion in the purpose of motion may be storedin the storage unit 220. The operation condition setting unit 242 caninclude and set various kinds of information related to the purpose ofmotion as the purpose of motion.

Further, the user may appropriately set the method of setting thepurpose of motion through the operation condition setting unit 242, forexample, according to the purpose of the robot arm apparatus 10.Further, the operation condition setting unit 242 may set the purpose ofmotion and the constraint condition by appropriately combining the abovemethods. Furthermore, a priority of the purpose of motion may be set tothe constraint condition stored in the storage unit 220, and when thereare a plurality of different purposes of motion, the operation conditionsetting unit 242 may set the purpose of motion according to the priorityof the constraint condition. The operation condition setting unit 242transmits the arm state, the set purpose of motion and the constraintcondition to the virtual force calculating unit 243.

The virtual force calculating unit 243 calculates virtual force in theoperation related to the whole body cooperative control using thegeneralized inverse dynamics. For example, a virtual force calculationprocess performed by the virtual force calculating unit 243 may be aseries of processes described above in (2-2-1. Virtual force calculatingprocess). The virtual force calculating unit 243 transmits thecalculated virtual force f_(v) to the actual force calculating unit 244.

The actual force calculating unit 244 calculates actual force in theoperation related to the whole body cooperative control using thegeneralized inverse dynamics. For example, an actual force calculationprocess performed by the actual force calculating unit 244 may be aseries of processes described above in (2-2-2. Actual force calculatingprocess). The actual force calculating unit 244 transmits the calculatedactual force (the generated torque) τ_(a) to the ideal joint controlunit 250. Further, in the present embodiment, the generated torque τ_(a)calculated by the actual force calculating unit 244 is also referred toas a “control value” or a “control torque value” to mean a control valueof the joint unit 130 in the whole body cooperative control.

The ideal joint control unit 250 performs various kinds of operationsrelated to the ideal joint control based on the generalized inversedynamics. In the present embodiment, the ideal joint control unit 250corrects influence of a disturbance on the generated torque τ_(a)calculated by the actual force calculating unit 244, and calculates thetorque command value τ for implementing the ideal response of the armunit 120. The operation process performed by the ideal joint controlunit 250 corresponds to a series of processes described above in [2-3.Ideal joint control].

The ideal joint control unit 250 includes a disturbance estimating unit251 and a command value calculating unit 252.

The disturbance estimating unit 251 calculates the disturbanceestimation value τ_(d) based on the torque command value τ and therotational angular velocity calculated from the rotational angle qdetected by the rotational angle detecting unit 133. Here, the torquecommand value τ refers to the command value indicating the generatedtorque of the arm unit 120 that is finally transmitted to the robot armapparatus 10. As described above, the disturbance estimating unit 251has a function corresponding to the disturbance observer 620 illustratedin FIG. 5.

The command value calculating unit 252 calculates the torque commandvalue τ serving as the command value indicating torque that is generatedby the arm unit 120 and finally transmitted to the robot arm apparatus10 using the disturbance estimation value τ_(d) calculated by thedisturbance estimating unit 251. Specifically, the command valuecalculating unit 252 calculates the torque command value τ by adding thedisturbance estimation value τ_(d) calculated by the disturbanceestimating unit 251 to τ^(ref) calculated from the ideal model of thejoint unit 130 expressed by Equation (12). For example, when thedisturbance estimation value τ_(d) is not calculated, the torque commandvalue τ is used as the torque target value τ^(ref). As described above,the function of the command value calculating unit 252 corresponds to afunction other than that of the disturbance observer 620 illustrated inFIG. 5.

As described above, in the ideal joint control unit 250, a series ofprocesses described above with reference to FIG. 5 is performed suchthat information is repeatedly exchanged between the disturbanceestimating unit 251 and the command value calculating unit 252. Theideal joint control unit 250 transmits the calculated torque commandvalue τ to the drive control unit 111 of the robot arm apparatus 10. Thedrive control unit 111 performs control of supplying an amount ofelectric current corresponding to the transmitted torque command value τto the motor in the actuator of the joint unit 130, controls the numberof revolutions of the motor, and controls the rotational angle and thegenerated torque of the joint unit 130.

In the robot arm control system 1 according to the present embodiment,since driving control of the arm unit 120 in the robot arm apparatus 10is continuously performed while a task using the arm unit 120 is beingperformed, the above-described process is repeatedly performed in therobot arm apparatus 10 and the control device 20. In other words, thejoint state detecting unit 132 of the robot arm apparatus 10 detects thestate of the joint unit 130, and transmits the detected state of thejoint unit 130 to the control device 20. In the control device 20,various kinds of operations related to the whole body cooperativecontrol and the ideal joint control for controlling driving of the armunit 120 are performed based on the state of the joint unit 130, thepurpose of motion, and the constraint condition, and the torque commandvalue τ serving as the operation result is transmitted to the robot armapparatus 10. In the robot arm apparatus 10, driving of the arm unit 120is controlled based on the torque command value τ, and the state of thejoint unit 130 during or after driving is detected by the joint statedetecting unit 132 again.

The description of the other components of the control device 20 willnow continue.

The input unit 210 is an input interface through which the user inputs,for example, information or a command related to driving control of therobot arm apparatus 10 to the control device 20. In the presentembodiment, based on an operation input from the input unit 210 by theuser, driving of the arm unit 120 of the robot arm apparatus 10 may becontrolled, and the position and posture of the imaging unit 140 may becontrolled. Specifically, as described above, as the user inputsinstruction information related to an instruction of arm driving inputfrom the input unit 210 to the operation condition setting unit 242, theoperation condition setting unit 242 may set the purpose of motion inthe whole body cooperative control based on the instruction information.As described above, the whole body cooperative control is performedusing the purpose of motion based on the instruction information inputby the user, and thus driving of the arm unit 120 according to theuser's operation input is implemented.

Specifically, the input unit 210 includes an operation unit operated bythe user such as a mouse, a keyboard, a touch panel, a button, a switch,a lever, and a pedal, for example. For example, when the input unit 210includes a pedal, the user can control driving of the arm unit 120 byoperating the pedal by foot. Thus, even when the user performs atreatment on the patient's medical procedure part using both hands, itis possible to adjust the position and posture of the imaging unit 140,that is, the photographing position or the photographing angle of themedical procedure part through an operation of the pedal by foot.

The storage unit 220 stores various kinds of pieces of information thatare processed by the control device 20. In the present embodiment, thestorage unit 220 can store various kinds of parameters used in theoperation related to the whole body cooperative control and the idealjoint control performed by the control unit 230. For example, thestorage unit 220 may store the purpose of motion and the constraintcondition used in the operation related to the whole body cooperativecontrol performed by the whole body cooperative control unit 240. Thepurpose of motion stored in the storage unit 220 may be a purpose ofmotion that can be set in advance so that the imaging unit 140 can stopat a certain point in the space as described above, for example.Further, the constraint condition may be set by the user in advanceaccording to the geometric configuration of the arm unit 120, thepurpose of the robot arm apparatus 10, or the like and then stored inthe storage unit 220. Furthermore, the storage unit 220 may storevarious kinds of information related to the arm unit 120 used when thearm state acquiring unit 241 acquires the arm state. Moreover, thestorage unit 220 may store, for example, the operation result in theoperation related to the whole body cooperative control and the idealjoint control performed by the control unit 230 and numerical valuescalculated in the operation process. As described above, the storageunit 220 may store all parameters related to various kinds of processesperformed by the control unit 230, and the control unit 230 can performvarious kinds of processes while transmitting or receiving informationto or from the storage unit 220.

The function and configuration of the control device 20 have beendescribed above. The control device 20 according to the presentembodiment may be configured, for example, with various kinds ofinformation processing devices (arithmetic processing devices) such as apersonal computer (PC) or a server. Next, a function and configurationof the display device 30 will be described.

The display device 30 displays various kinds of information on thedisplay screen in various formats such as text or an image, and visuallynotifies the user of the information. In the present embodiment, thedisplay device 30 displays an image captured by the imaging unit 140 ofthe robot arm apparatus 10 through the display screen. Specifically, thedisplay device 30 includes a function or component such as an imagesignal processing unit (not illustrated) that performs various kinds ofimage processing on the image signal acquired by the imaging unit 140 ora display control unit (not illustrated) that performs control such thatan image based on the processed image signal is displayed on the displayscreen. Further, the display device 30 may have various kinds offunctions and components that are equipped in a general display devicein addition to the above function or component. The display device 30corresponds to the display device 550 illustrated in FIG. 1.

The functions and configurations of the robot arm apparatus 10, thecontrol device 20, and the display device 30 according to the presentembodiment have been described above with reference to FIG. 6. Each ofthe above components may be configured using a versatile member orcircuit, and may be configured by hardware specialized for the functionof each component. Further, all the functions of the components may beperformed by a CPU or the like. Thus, a configuration to be used may beappropriately changed according to a technology level when the presentembodiment is carried out.

As described above, according to the present embodiment, the arm unit120 having the multi-link structure in the robot arm apparatus 10 has atleast 6 or more degrees of freedom, and driving of each of the pluralityof joint units 130 configuring the arm unit 120 is controlled by thedrive control unit 111. Further, the medical apparatus is installed atthe front edge of the arm unit 120. As driving of each joint unit 130 iscontrolled as described above, driving control of the arm unit 120having a high degree of freedom is implemented, and the robot armapparatus 10 for medical use having high operability for a user isimplemented.

More specifically, according to the present embodiment, in the robot armapparatus 10, the state of the joint unit 130 is detected by the jointstate detecting unit 132. Further, in the control device 20, based onthe state of the joint unit 130, the purpose of motion, and theconstraint condition, various kinds of operations related to the wholebody cooperative control using the generalized inverse dynamics forcontrolling driving of the arm unit 120 are performed, and torquecommand value τ serving as the operation result are calculated.Furthermore, in the robot arm apparatus 10, driving of the arm unit 120is controlled based on the torque command value τ. As described above,in the present embodiment, driving of the arm unit 120 is controlled bythe whole body cooperative control using the generalized inversedynamics. Thus, driving control of the arm unit 120 according to theforce control is implemented, and the robot arm apparatus having thehigh operability for the user is implemented. Further, in the presentembodiment, in the whole body cooperative control, for example, controlfor implementing various kinds of purposes of motion for improving userconvenience such as the pivot movement and the power assist movement canbe performed. Furthermore, in the present embodiment, for example,various driving units for moving the arm unit 120 manually or through anoperation input from a pedal are implemented, and thus user convenienceis further improved.

Further, in the present embodiment, the whole body cooperative controland the ideal joint control are applied to driving control of the armunit 120. In the ideal joint control, a disturbance component such asfriction or inertia in the joint unit 130 is estimated, and feedforwardcontrol is performed using the estimated disturbance component. Thus,even when there is a disturbance component such as friction, the idealresponse can be implemented on driving of the joint unit 130. Thus,small influence of vibration or the like, high-accuracy responsiveness,and high positioning accuracy or stability are implemented in drivingcontrol of the arm unit 120.

Further, in the present embodiment, each of the plurality of joint units130 configuring the arm unit 120 has a configuration suitable for theideal joint control illustrated in FIG. 3, for example, and therotational angle, the generated torque and the viscous drag coefficientof each of the joint units 130 can be controlled according to anelectric current value. As described above, driving of each of the jointunits 130 is controlled according to an electric current value, anddriving of each of the joint units 130 is controlled according to thewhole body cooperative control while detecting the entire state of thearm unit 120, and thus the counter balance is unnecessary, and the smallrobot arm apparatus 10 is implemented.

[2-5. Specific Example of Purpose of Motion]

Next, a specific example of the purpose of motion according to thepresent embodiment will be described. As described above in [2-4.Configuration of the robot arm control system], in the presentembodiment, various kinds of purposes of motion are implemented by thewhole body cooperative control. Here, as a specific example of thepurpose of motion according to the present embodiment, the power assistmovement and the pivot movement will be described. In the followingdescription of the specific example of the purpose of motion, componentsof the robot arm control system according to the present embodiment areindicated using reference numerals in the functional block diagramillustrated in FIG. 6.

The power assist movement is a movement of controlling the state of thejoint unit 130 such that gravity acting on the arm unit 120 is negatedand controlling the state of the joint unit 130 such that movement ofthe arm unit 120 in a direction of force applied from the outside issupported. Specifically, when the user manually moves the arm unit 120,the power assist movement is a movement of controlling driving of thearm unit 120 such that force applied by the user is supported. Morespecifically, in order to implement the power assist movement, first,external torque is detected by the torque detecting unit 134 in a statein which no force other than gravity acts on the arm unit 120, and theinstantaneous purpose of motion is set so that the generated torque fornegating the detected external torque is generated by each of the jointunits 130. At this stage, the position and posture of the arm unit 120are held in a certain state. When external torque is further appliedfrom the outside (for example, from the user) in this state,additionally applied external torque is detected by the torque detectingunit 134, and the instantaneous purpose of motion is further set suchthat each of the joint units 130 generates generated torque in the samedirection as the detected additional external torque. As driving of eachof the joint units 130 is controlled according to the instantaneouspurpose of motion, the power assist movement is implemented. Through thepower assist movement, the user can move the arm unit by small force,and thus the user can have a feeling of moving the arm unit 120 in anon-gravity state, and the operability of the arm unit 120 by the useris improved.

The pivot movement is a turning movement in which the front edge unitinstalled at the front edge of the arm unit 120 moves on a plane of acone having a certain point in the space as an apex in a state in whicha direction of the front edge unit is fixed on the certain point, and anaxis of the cone is used as a pivot axis. Specifically, when the frontedge unit is the imaging unit 140, the pivot movement is a turningmovement in which the imaging unit 140 installed at the front edge ofthe arm unit 120 moves on a plane of a cone having a certain point in aspace as an apex in a state in which the photographing direction of theimaging unit 140 is fixed on the certain point, and an axis of the coneis used as a pivot axis. As a point corresponding to the apex of thecone in the pivot movement, for example, the medical procedure part isselected. Further, in the pivot movement, the turning movement may beperformed in a state in which a distance between the front edge unit orthe imaging unit 140 and the point corresponding to the apex of the coneis maintained constant. Further, since the direction of the front edgeunit or the photographing direction of the imaging unit 140 is fixed ona certain point (for example, the medical procedure part) in the space,the pivot movement is also referred to as a “point lock movement.”

<3. Control According to Visual Field Enlargement Factor>

Next, control according to a visual field enlargement factor will bedescribed. In the present embodiment, the usability of the robot arm bythe user is adjusted according to the on-screen enlargement factor of asubject imaged by the imaging unit 140 (hereinafter, the visual fieldenlargement factor may be designated simply the enlargement factor insome cases). FIG. 7 is a schematic diagram illustrating a configurationof a specific system 1000 that adjusts a usability of a robot armaccording to a visual field enlargement factor. The system 1000illustrated in FIG. 7 includes a central processing unit (CPU) 1100, acamera 1200, an operation input unit 1300, a sensor 1400, motor controlunits 1500 a, 1500 b, 1500 f, encoders 1600 a, 1600 b, . . . , 1600 f,motors 1700 a, 1700 b, . . . , 1700 f, and torque sensors 1800 a, 1800b, . . . , 1800 f.

The camera 1400 illustrated in FIG. 7 corresponds to the imaging unit140 in FIG. 6. In addition, the encoder 1600 a, the motor 1700 a, andthe torque sensor 1800 a constitute the joint unit 421 a. Similarly, theencoder 1600 b, the motor 1700 b, and the torque sensor 1800 bconstitute the joint unit 421 b, while the encoder 1600 f, the motor1700 f, and the torque sensor 1800 f constitute the joint unit 421 f.

The operation input unit 1300 corresponds to the input unit 210 in FIG.6. The operation input unit 1300 is a switch, such as a remote controlswitch or a foot switch, for example. The sensor 1400 is mounted to thefront edge of the arm unit 120 of the robot arm apparatus 10, forexample, and is a sensor such as six-axis sensor that detects useroperations.

Additionally, the central processing unit 1100 illustrated in FIG. 7corresponds to the control unit 230 in FIG. 6. Also, each of the motorcontrol units 1500 a, 1500 b, . . . , 1500 f correspond to the armcontrol unit 110 in FIG. 6.

Additionally, the encoders 1600 a, 1600 b, . . . , 1600 f includedrespectively in the joint units 421 a, 421 b, . . . , 421 c correspondto the rotational angle detecting unit 133 in FIG. 6, while the motors1800 a, 1800 b, . . . , 1800 f included respectively in the joint units421 a, 421 b, . . . , 421 f correspond to the joint driving unit 131 inFIG. 6, and the torque sensors 1800 a, 1800 b, . . . , 1800 f includedrespectively in the joint units 421 a, 421 b, . . . , 421 f correspondto the torque detecting unit 134 in FIG. 6.

In the robot arm apparatus 10, the case of a high enlargement factor ofan image captured by the camera 1200 is a state in which the subject isgreatly enlarged. In such a state, since the operator is observing theenlarged subject more carefully, it is not preferable for the arm unit120 of the robot arm apparatus 10 to move unexpectedly.

For this reason, in the present embodiment, the motion of each of thejoint units 421 a, 421 b, . . . , 421 f is controlled according to theenlargement factor. Specifically, the viscosity of the motion of each ofthe joint units 421 a, 421 b, . . . , 421 f is controlled according tothe enlargement factor. Additionally, the velocity of the motion and theamount of movement with respect to an operation of each of the jointunits 421 a, 421 b, . . . , 421 f are controlled according to theenlargement factor. The visual field enlargement factor may becalculated from distance information about the distance from the camera1200 to the imaging target (subject) and the zoom factor (imagingmagnification) of the camera 1200. Also, for the distance information tothe subject, distance information according to autofocus obtained fromthe camera 1200, distance information according to stereo vision,distance information estimated from the arm orientation, distanceinformation measured by some other sensor, such as a rangefinder sensor,or the like may be used. For example, if the zoom factor is at maximumand the camera 1200 is maximally close to the object, control that movesthe slowest may be performed (that is, the lowest drive velocity or thehighest viscosity is set), whereas if the distance between the camera1200 and the subject is large, even under zoomed imaging, and a widerange is visible, operability is not reduced even with a high drivevelocity or a low viscosity. When driving the joints, it is preferableto adjust the drive velocity and viscosity so that the rate of movementof the object always stays within a certain range, regardless of theapparent size of the object on-screen.

With viscosity control, control is performed to raise the viscosity ofthe motion of each of the joint units 421 a, 421 b, . . . , 421 f to theextent that the enlargement factor by the camera 1200 is high. As theviscosity of the motion of each of the joint units 421 a, 421 b, 421 frises, an opposing force corresponding to the movement of the arm unit120 is imparted to the operator, and the motion of the arm becomessluggish. Thus, fine adjustment of the front edge of the arm unit 120becomes easier to perform. Consequently, the operator is able to makefine adjustments to the position of the camera 1200 with respect to thesubject while checking an enlarged picture of the subject on the displaydevice 30.

To control motion as above, information related to the enlargementfactor is sent from the camera 1200 to the central processing unit 1100.In the central processing unit 1100, the operation condition settingunit 242 computes a value of viscosity according to the enlargementfactor as the purpose of motion discussed earlier. Additionally, theprocesses discussed earlier are performed by the virtual forcecalculating unit 243 and the actual force calculating unit 244, aprocess is performed by the ideal joint control unit 250, and inaddition, a torque command value τ is computed based on the computedvalue of viscosity, and sent to each of the motor control units 1500 a,1500 b, . . . , 1500 c. The motor control units 1500 a, 1500 b, . . . ,1500 f respectively control the motors 1700 a, 1700 b, . . . , 1700 fbased on the torque command value τ. As discussed earlier, the motordriver 425 of the robot arm apparatus 10 is able to adjust a viscousdrag coefficient on rotary motion of the actuator 430 by adjusting theamount of current supplied to the motor 424.

FIG. 8 is a schematic diagram illustrating an example of a map to usewhen the central processing unit 1100 computes a viscosity according toan enlargement factor. As illustrated in FIG. 8, a map is prescribed sothat as the enlargement factor increases, the value of viscosity alsoincreases. Also, as illustrated in FIG. 8, in cases such as when therobot arm apparatus 10 is used for medical surgery, different mapcharacteristics may be prescribed depending on the surgical procedure.Consequently, in Procedure 1, which demands more high-precisionoperation of the robot arm apparatus 10, the ratio of the increase inviscosity with respect to the increase in enlargement factor is raised,thereby making it possible to make the motion of the arm unit 120 of therobot arm apparatus 10 more sluggish to make more high-precision fineadjustments. Note that the map illustrated in FIG. 8 may be stored inmemory provided in the control device 20. Also, in FIG. 8, an example ofswitching the map depending on the surgical procedure is illustrated,but the map may also be switched in response to a user operationperformed on the operation input unit 1300. Consequently, the user isable to set the motion (viscosity) of the arm unit 120 to the user'spreferred state.

Additionally, when controlling velocity according to the enlargementfactor, control is performed to lower the velocity of the motion of eachof the joint units 421 a, 421 b, . . . , 421 f to the extent that theenlargement factor by the camera 1200 is high. Consequently, since thevelocity of the motion of each of the joint units 421 a, 421 b, . . . ,421 f lowers as the enlargement factor rises, more high-precision fineadjustment of the arm unit 120 of the robot arm apparatus 10 becomespossible.

Similarly, when controlling the amount of movement with respect to anoperation according to the enlargement factor, control is performed todecrease the amount of movement of the front edge of the arm unit 120 ofthe robot arm apparatus 10 to the extent that the enlargement factor bythe camera 1200 is high. Consequently, since the amount of movement inthe motion of each of the joint units 421 a, 421 b, . . . , 421 f lowersas the enlargement factor rises, more high-precision fine adjustment ofthe robot arm apparatus 10 becomes possible.

When controlling the velocity and the amount of movement according tothe enlargement factor, the operation condition setting unit 242computes the velocity and the amount of movement according to theenlargement factor as the purpose of motion discussed earlier. Thevelocity and the amount of movement according to the enlargement factormay be computed from the map illustrated in FIG. 14, for example. Asillustrated in FIG. 14, the velocity and the amount of movement loweraccording to the enlargement factor. Additionally, the processesdiscussed earlier are performed by the virtual force calculating unit243 and the actual force calculating unit 244, a process is performed bythe ideal joint control unit 250, and a torque command value τ is outputfrom the command value calculating unit 252 to the robot arm apparatus10. The torque command value τ is sent to each of the motor controlunits 1500 a, 1500 b, . . . , 1500 f. The motor control units 1500 a,1500 b, . . . , 1500 f respectively control the motors 1700 a, 1700 b, .. . , 1700 f based on the torque command value τ. Note that the amountof movement may refer to the amount of movement of the arm unit 120corresponding to a single operation in the case in which the userperforms remote control operations on the arm unit 120 using theoperation input unit 1300, for example.

As above, in the present embodiment, by switching the viscosity, themovement velocity, the amount of movement (amount of movement of the armunit 120 with respect to a single operation by the user), theacceleration, or other parameters according to the enlargement factor ofthe camera 1400, an opposing force according to the amount of movementof the arm unit 120 by a user operation may be returned to the operator,and operability may be improved. Consequently, when the enlargementfactor is high, more fine-grained adjustments become possible. Also,when the enlargement factor is low, the arm unit 120 becomes easier tomove, thereby making it possible to move the arm unit 120 rapidly sothat a desired part of the subject is displayed on the display device30.

In addition, control is also possible in which orientation informationabout the arm unit 120 is utilized and the viscosity is increasedaccording to a magnitude shifted from a fixed distance, for example, inorder to keep the distance between the subject and the front edge of thearm unit 120 a fixed distance.

Control according to the enlargement factor basically is performed whenoperating input from the user is detected. The detection of operatinginput may be conducted by detecting user operations performed on theoperation input unit 1300 (primarily remote control operations). Also,the detection of operating input may be detected by the torque sensors1800 a, 1800 b, . . . , 1800 f when the user operates the arm unit 120.In addition, by sensing external force, it is also possible to switchfrom a state in which the arm unit 120 is locked to a mode in which thearm unit 120 moves with light operating force. If an electromagneticbrake function is included, the disengagement (or engagement) of theelectromagnetic brake may also be conducted in conjunction with thestate switch. Additionally, it is also possible to sense not onlyoperations in the XY directions of the screen of the display device 30,but also force in the Z direction (the depth direction of the screen),and control the viscosity, velocity, acceleration, or amount ofmovement, or detect an operation in any of the XYZ directions withrespect to the screen and change the focus position, the enlargementfactor, or the camera position.

Detection of external force may include not only detection using thetorque sensors 1800 a, 1800 b, . . . , 1800 f respectively built intoeach of the joint units 421 a, 421 b, . . . , 421 f, but may also bedetected using a sensor such as a touch sensor installed on the arm unit120, or a six-axis force sensor or a proximity sensor installed at thebase or one the front edge of the arm unit 120. These sensors areincluded in the sensor 1400 illustrated in FIG. 7.

Additionally, the respective encoders 1600 a, 1600 b, . . . , 1600 f ofthe joint units 421 a, 421 b, . . . , 421 f may be utilized topseudo-detect that the arm has been operated, based on positioninformation and angular velocity detected from the encoders 1600 a, 1600b, . . . , 1600 f.

In addition, an operation by the operator may be not only an operationof moving the arm unit 120 directly, but also be detected by a sensorsuch as an infrared proximity sensor. Also, contactless operations usingvoice input, gestures, or hand movements are also possible.

In this way, the operation input unit 1300 may also be a sensor thatdetects speech, or a sensor (six-axis force sensor) that detectscontactless operations such as gestures or hand movements.

In the case of inputting operation information from the operation inputunit 1300 with a remote control, components such as mechanical switches,jog dials, and analog sticks may be used as the operation input unit1300. Furthermore, in the case of a configuration that works inconjunction with medical navigation, in which a target position of thearm unit 120 is input separately, for example, it is also possible toraise the viscosity when the front edge of the arm unit 120 comes closeto the target position, and thereby notify the operator that the frontedge has come near the target position.

In addition, various sensors that detect properties such as gaze,speech, brain wave, and facial expressions may be used as the sensor1400. The arm unit 120 may be controlled based on detections by thesesensors.

If there is interference, such as interference with an organ in the casein which the front edge of the robot arm apparatus 10 is used inside thebody, or interference between the robot arm apparatus 10 and a tool orthe like outside the body, it is also possible to suspend or make lessresponsive the movement of the arm unit 120, and by raising the opposingforce and viscosity of the arm unit 120, notify the operator of theinterference, and potentially improve safety.

<4. Processing Procedure of Robot Arm Control Method>

Next, a processing procedure of a robot arm control method according toan embodiment of the present disclosure will be described with referenceto FIG. 9. FIG. 9 is a flowchart illustrating a processing procedure ofa robot arm control method according to an embodiment of the presentdisclosure. The following description will proceed with an example inwhich the robot arm control method according to the present embodimentis implemented through the configuration of the robot arm control system1 illustrated in FIG. 6. Thus, the robot arm control method according tothe present embodiment may be a medical robot arm control method.Further, in the following description of the processing procedure of therobot arm control method according to the present embodiment, thefunctions of the respective components of the robot arm control system 1illustrated in FIG. 6 have already been described above in [2-4.Configuration of the robot arm control system], and thus a detaileddescription thereof is omitted.

Referring to FIG. 9, in the robot arm control method according to thepresent embodiment, first, in step S801, the joint state detecting unit132 detects the state of the joint unit 130. Here, the state of thejoint unit 130 refers to, for example, the rotational angle, thegenerated torque and/or the external torque in the joint unit 130.

Then, in step S803, the arm state acquiring unit 241 acquires the armstate based on the state of the joint unit 130 detected in step S801.The arm state refers to a motion state of the arm unit 120, and may be,for example, a position, a speed, or acceleration of each component ofthe arm unit 120, or force acting on each component of the arm unit 120.

Then, in step S805, the operation condition setting unit 242 sets thepurpose of motion and the constraint condition used for the operation inthe whole body cooperative control based on the arm state acquired instep S803. Further, the operation condition setting unit 242 may not setthe purpose of motion based on the arm state, may set the purpose ofmotion based on the instruction information on driving of the arm unit120 which is input, for example, from the input unit 210 by the user,and may use the purpose of motion previously stored in the storage unit220. Furthermore, the purpose of motion may be set by appropriatelycombining the above methods. Moreover, the operation condition settingunit 242 may use the constraint condition previously stored in thestorage unit 220.

Then, in step S807, the operation for the whole body cooperative controlusing the generalized inverse dynamics is performed based on the armstate, the purpose of motion, and the constraint condition, and acontrol value τ_(a) is calculated. The process performed in step S807may be a series of processes in the virtual force calculating unit 243and the actual force calculating unit 244 illustrated in FIG. 6, thatis, a series of processes described above in [2-2. Generalized inversedynamics].

Then, in step S809, the disturbance estimation value τ_(d) iscalculated, the operation for the ideal joint control is performed usingthe disturbance estimation value τ_(d), and the command value τ iscalculated based on the control value τ_(a). The process performed instep S809 may be a series of processes in the ideal joint control unit250 illustrated in FIG. 6, that is, a series of processes describedabove in [2-3. Ideal joint control].

Lastly, in step S811, the drive control unit 111 controls driving of thejoint unit 130 based on the command value τ.

The processing procedure of the robot arm control method according tothe present embodiment has been described above with reference to FIG.9. In the present embodiment, the process of step S801 to step S811illustrated in FIG. 9 is repeatedly performed while the task using thearm unit 120 is being performed. Thus, in the present embodiment,driving control of the arm unit 120 is continuously performed while thetask using the arm unit 120 is being performed.

Next, a process of control according to the enlargement factor will bedescribed based on FIG. 10. First, in step S10, it is determined whetheror not operating input of at least a fixed value is detected. Thedetection of operating input is conducted by the respective torquesensors 1800 a, 1800 b, . . . , 1800 f of the joint units 421 a, 421 b,. . . , 421 f. Also, in cases such as when the arm unit 120 isremote-controlled, the detection of operating input may also beconducted by the operation input unit 1300.

In step S10, if it is determined that operating input of at least afixed value has been detected, the flow proceeds to step S12, and theenlargement factor of an image captured by the camera 1200 is acquired.Specifically, the central processing unit 1100 acquires the zoom factorfrom the camera 1200, and acquires the enlargement factor from the zoomfactor and distance information about the subject.

In the following step S14, the viscosity, the velocity, or the amount ofmovement according to the enlargement factor is calculated. As discussedabove, the viscosity, the velocity, and the amount of movement accordingto the enlargement factor may be computed from a map prescribing arelationship between the enlargement factor and these parameters.

In the next step S16, driving of the arm unit 120 by force control isstarted. At this point, since the viscosity, the velocity, or the amountof movement is controlled according to the enlargement factor, fineadjustment of the arm unit becomes possible to the extent that theenlargement factor is high. After step S16, the flow returns to stepS10.

Meanwhile, in the case of determining in step S10 that operating inputof at least a fixed value has not been detected, the flow proceeds tostep S18. In step S18, control locking the orientation of the arm unit120 to the current orientation is performed.

As above, according to the process in FIG. 10, if operating input of atleast a fixed value is detected, the viscosity, the movement velocity ofthe arm, or the amount of movement of the arm is controlled according tothe enlargement factor. Consequently, if the enlargement factor islarge, it becomes possible to increase the viscosity. Also, if theenlargement factor is large, control that decreases the movementvelocity or the amount of movement of the arm becomes possible.Consequently, if the enlargement factor is high, it becomes possible tomake more precise fine adjustments of the arm unit.

Next, control of the viscosity of the driving of a joint unit based onthe state of the joint unit will be described. As discussed above, inthe robot arm control method according to the present embodiment, thestate of the joint unit 130 is detected. Subsequently, based on thestate of the joint unit 130, the arm state is acquired by the arm stateacquiring unit 241. The arm state refers to the state of motion of thearm unit 120, and may be properties such as the position, the velocity,and the acceleration of each structural member of the arm unit 120, orthe force acting on each structural member of the arm unit 120, forexample.

The central processing unit 1100 controls the viscosity of the drivingof the joint unit 130 based on the state of the joint unit 130. Forexample, if the arm unit 120 moves in a certain predetermined direction,control is performed to raise the viscosity or lower the viscositycompared to normal. Also, if the arm unit 120 is in a certainpredetermined orientation, control is performed to raise the viscosityor lower the viscosity compared to normal. Also, if the arm unit 120moves at a certain predetermined velocity, control is performed to raisethe viscosity or lower the viscosity compared to normal.

In the central processing unit 1100, the arm state acquiring unit 241acquires the state of the joint unit 130 (arm state). The operationcondition setting unit 242 computes the value of viscosity according tothe state of the joint unit 130 as the purpose of motion discussedearlier. Additionally, the processes discussed earlier are performed bythe virtual force calculating unit 243 and the actual force calculatingunit 244, a process is performed by the ideal joint control unit 250,and in addition, a torque command value τ is computed based on thecomputed value of viscosity, and sent to each of the motor control units1500 a, 1500 b, . . . , 1500 c. The motor control units 1500 a, 1500 b,. . . , 1500 f respectively control the motors 1700 a, 1700 b, . . . ,1700 f based on the torque command value τ. As discussed earlier, themotor driver 425 of the robot arm apparatus 10 is able to adjust aviscous drag coefficient on rotary motion of the actuator 430 byadjusting the amount of current supplied to the motor 424.

Consequently, since the viscosity changes according to the direction,the orientation, and the velocity of the motion of the arm unit 120, themotion of the arm unit 120 may be made lighter or heavier in the case ofmotion in a certain direction or a certain orientation, and optimalmotion according to the operator's needs may be realized. Morespecifically, by changing the viscosity in a specific direction based onposition information obtained from the state of the joint unit 130, itis possible to make fine adjustments in just a specific direction easierto perform. For example, by raising the viscosity with respect to the XYdirections displayed on a screen, and making the viscosity heavier withrespect to the Z direction, it is possible to make operations only inthe XY directions easier to perform while also limiting motion in aspecific direction. Additionally, based on velocity information obtainedfrom the state of the joint unit 130, by switching so as to lower theviscosity and make movement easier when at least a certain speed isreached, the operator becomes able to select between the operability offine movement and large motion. Additionally, by adjusting the viscositybased on acceleration information obtained from the state of the jointunit 130, it is possible to move at a fixed velocity without beinginfluenced by the uneven application of manual force, thereby making iteasier to observe an affected area without requiring delicate and evenapplication of force. Additionally, by raising the viscosity to limitmotion in the direction proceeding towards an affected area of thepatient based on position information obtained from the state of thejoint unit 130, it becomes possible to allow operations in otherdirections while increasing safety.

Control of the viscosity based on the state of the joint unit 130 andcontrol of the viscosity based on the enlargement factor discussedearlier may also be conducted in combination with each other. In thiscase, the central processing unit 1100 controls the viscosity of thedriving of the joint unit 130 based on the state of the joint unit 130and the enlargement factor.

<5. Operation Matching On-Screen Directions>

Next, a technique of operating the arm unit 120 to match on-screen XYdirections according to the present embodiment will be described.According to the robot arm apparatus 10 according to the presentembodiment, if the joint unit 421 f is rotationally driven, the subjectmay be rotated with respect to the display screen of the display device30.

FIG. 11(A) illustrates the positional relationship between the subjectand the frame 30 a of the display device 30 before the joint unit 421 fis rotationally driven. Also, FIG. 11(B) illustrates the positionalrelationship between the subject and the frame 30 a of the displaydevice 30 after the joint unit 421 f is rotated. By causing the jointunit 421 f to rotated from the state in FIG. 11(A) to the state in FIG.11(B), the frame 30 a of the display device 30 rotates clockwise withrespect to the subject. In other words, the subject rotatescounter-clockwise with respect to the frame 30 a of the display device30.

On the other hand, suppose that while the joint unit 421 f rotates, thejoint units other than the joint unit 421 f are not operating. At thispoint, suppose a case in which, from the state in FIG. 11(B), the useroperates the operation input unit 1300, and moves the arm unit 120 byremote control. In the case of operating the arm in the Y axis directionin FIG. 11(B), if the robot arm apparatus 10 does not account for therotation of the display frame 30 a from FIG. 11(A) to FIG. 11(B), therobot arm apparatus 10 will recognize the operation as being performedin the Y axis direction illustrated in FIG. 11(A). For this reason, thedisplay frame 30 a moves in the Y′ axis direction in FIG. 11(B).Consequently, the direction in which the operator is attempting to movethe arm unit 120 on the display screen becomes different from the actualmovement direction of the arm unit 120, which feels unnatural to theoperator who is performing operations while looking at the displayscreen, and also reduces operability.

For this reason, in the present embodiment, a process that realizes armmotion matching the on-screen directions is conducted. Specifically, theangular position of the camera 1200 with respect to the subject isacquired, and when the angular position of the camera 1200 with respectto the subject changes, the operation direction is corrected whileaccounting for the magnitude of the change. In the example of FIG. 11,when transitioning from FIG. 11(A) to FIG. 11(B), the camera 1200rotates by an angle θ, and the subject rotates by the angle θ withrespect to the frame 30 a of the display screen. Thus, for an operationdirection input by the user, the direction in which the arm unit 120 isto move is corrected by the angle θ. Consequently, when the userperforms an operation in the Y axis direction in FIG. 11(B), the armunit 120 moves in the Y axis direction, and thus the direction in whichthe arm unit 120 moves matches the operation direction on the displayscreen, thereby making it possible to increase operability greatly.

FIG. 12 is a flowchart illustrating a process of operating the arm unitto match the on-screen XY directions illustrated in FIG. 11. First, instep S20, the rotation angle θ of the camera 1200 is detected. At thispoint, the angle θ illustrated in FIG. 11(B) is computed. The angle θmay be computed from the encoder 1600 f of the joint unit 421 f.

In the following step S22, an operation direction input into theoperation input unit 1300 by the user is detected. As described usingFIG. 11(B), even if the user performs an operation in the Y axisdirection on the screen in FIG. 11(B), the robot arm apparatus 10recognizes the operation as an operation in the Y′ axis direction.

In the following step S24, the operation direction input into theoperation input unit 1300 by the user is corrected by the angle θ. As aresult, in FIG. 11(B), the operation direction is corrected from the Y′axis direction to the Y axis direction. In the following step S26, thearm unit 120 is driven in the corrected operation direction.

As above, by deciding the operation direction while accounting for therotation angle θ of the camera 1200, it becomes possible to make theoperation direction specified on-screen by the user match the actualoperation direction of the arm unit 120. Consequently, the user becomesable to perform operations intuitively while looking at the screen,making it possible to greatly improve operability.

<6. Hardware Configuration>

Next, a hardware configuration of the robot arm apparatus 10 and thecontrol device 20 according to the present embodiment illustrated inFIG. 6 will be described in detail with reference to FIG. 13. FIG. 13 isa functional block diagram illustrating an exemplary configuration of ahardware configuration of the robot arm apparatus 10 and the controldevice 20 according to an embodiment of the present disclosure.

The robot arm apparatus 10 and the control device 20 mainly include aCPU 901, a ROM 903, and a RAM 905. The robot arm apparatus 10 and thecontrol device 20 further include a host bus 907, a bridge 909, anexternal bus 911, an interface 913, an input device 915, an outputdevice 917, a storage device 919, a drive 921, a connection port 923,and a communication device 925.

The CPU 901 functions as an arithmetic processing device and a controldevice, and controls all or some operations of the robot arm apparatus10 and the control device 20 according to various kinds of programsrecorded in the ROM 903, the RAM 905, the storage device 919, or aremovable storage medium 927. The ROM 903 stores a program, an operationparameter, or the like used by the CPU 901. The RAM 905 primarily storesa program used by the CPU 901, a parameter that appropriately changes inexecution of a program, or the like. The above-mentioned components areconnected with one another by the host bus 907 configured with aninternal bus such as a CPU bus. The CPU 901 corresponds to, for example,6 the arm control unit 110 and the control unit 230 illustrated in FIG.6 in the present embodiment.

The host bus 907 is connected to the external bus 911 such as aperipheral component interconnect/interface (PCI) bus through the bridge909. Further, the input device 915, the output device 917, the storagedevice 919, the drive 921, the connection port 923, and thecommunication device 925 are connected to the external bus 911 via theinterface 913.

The input device 915 is an operating unit used by the user such as amouse, a keyboard, a touch panel, a button, a switch, a lever, or apedal. For example, the input device 915 may be a remote control unit (aso-called remote controller) using infrared light or any other radiowaves, and may be an external connection device 929 such as a mobiletelephone or a PDA corresponding to an operation of the robot armapparatus 10 and the control device 20. Further, for example, the inputdevice 915 is configured with an input control circuit that generates aninput signal based on information input by the user using the operatingunit, and outputs the input signal to the CPU 901. The user of the robotarm apparatus 10 and the control device 20 can input various kinds ofdata to the robot arm apparatus 10 and the control device 20 or instructthe robot arm apparatus 10 and the control device 20 to perform aprocessing operation by operating the input device 915. For example, theinput device 915 corresponds to the input unit 210 illustrated in FIG. 6in the present embodiment. Further, in the present embodiment, thepurpose of motion in driving of the arm unit 120 may be set by anoperation input through the input device 915 by the user, and the wholebody cooperative control may be performed according to the purpose ofmotion.

The output device 917 is configured with a device capable of visually oracoustically notifying the user of the acquired information. As such adevice, there are a display device such as a CRT display device, aliquid crystal display device, a plasma display device, an EL displaydevice or a lamp, an audio output device such as a speaker or aheadphone, a printer device, and the like. For example, the outputdevice 917 outputs a result obtained by various kinds of processesperformed by the robot arm apparatus 10 and the control device 20.Specifically, the display device displays a result obtained by variouskinds of processes performed by the robot arm apparatus 10 and thecontrol device 20 in the form of text or an image. Meanwhile, the audiooutput device converts an audio signal including reproduced audio data,acoustic data, or the like into an analogue signal, and outputs theanalogue signal. In the present embodiment, various kinds of informationrelated to driving control of the arm unit 120 may be output from theoutput device 917 in all forms. For example, in driving control of thearm unit 120, the trajectory of movement of each component of the armunit 120 may be displayed on the display screen of the output device 917in the form of a graph. Further, for example, the display device 30illustrated in FIG. 6 may be a device including the function andconfiguration of the output device 917 serving as the display device anda component such as a control unit for controlling driving of thedisplay device.

The storage device 919 is a data storage device configured as anexemplary storage unit of the robot arm apparatus 10 and the controldevice 20. For example, the storage device 919 is configured with amagnetic storage unit device such as a hard disk drive (HDD), asemiconductor storage device, an optical storage device, a magnetooptical storage device, or the like. The storage device 919 stores aprogram executed by the CPU 901, various kinds of data, and the like.For example, the storage device 919 corresponds to the storage unit 220illustrated in FIG. 6 in the present embodiment. Further, in the presentembodiment, the storage device 919 may store the operation condition(the purpose of motion and the constraint condition) in the operationrelated to the whole body cooperative control using the generalizedinverse dynamics, and the robot arm apparatus 10 and the control device20 may perform the operation related to the whole body cooperativecontrol using the operation condition stored in the storage device 919.

The drive 921 is a recording medium reader/writer, and is equipped in orattached to the robot arm apparatus 10 and the control device 20. Thedrive 921 reads information stored in the removable storage medium 927mounted thereon such as a magnetic disk, an optical disc, a magnetooptical disc, or a semiconductor memory, and outputs the readinformation to the RAM 905. Further, the drive 921 can write a record inthe removable storage medium 927 mounted thereon such as a magneticdisk, an optical disk, a magneto optical disk, or a semiconductormemory. For example, the removable storage medium 927 is a DVD medium,an HD-DVD medium, a Blu-ray (a registered trademark) medium, or thelike. Further, the removable storage medium 927 may be a Compact Flash(CF) (a registered trademark), a flash memory, a Secure Digital (SD)memory card, or the like. Furthermore, for example, the removablestorage medium 927 may be an integrated circuit (IC) card equipped witha non-contact type IC chip, an electronic device, or the like. In thepresent embodiment, various kinds of information related to drivingcontrol of the arm unit 120 is read from various kinds of removablestorage media 927 or written in various kinds of removable storage media927 through the drive 921.

The connection port 923 is a port for connecting a device directly withthe robot arm apparatus 10 and the control device 20. As an example ofthe connection port 923, there are a Universal Serial Bus (USB) port, anIEEE1394 port, a Small Computer System Interface (SCSI) port, and thelike. As another example of the connection port 923, there are anRS-232C port, an optical audio terminal, a High-Definition MultimediaInterface (HDMI) (a registered trademark), and the like. As the externalconnection device 929 is connected to the connection port 923, the robotarm apparatus 10 and the control device 20 acquire various kinds of datadirectly from the external connection device 929 or provide variouskinds of data to the external connection device 929. In the presentembodiment, various kinds of information related to driving control ofthe arm unit 120 may be read from various kinds of external connectiondevices 929 or written in various kinds of external connection devices929 through the connection port 923.

For example, the communication device 925 is a communication interfaceconfigured with a communication device used for a connection with acommunication network (network) 931. For example, the communicationdevice 925 is a communication card for a wired or wireless local areanetwork (LAN), Bluetooth (a registered trademark), or wireless USB(WUSB). Further, the communication device 925 may be an opticalcommunication router, an asymmetric digital subscriber line (ADSL)router, various kinds of communication modems, or the like. For example,the communication device 925 can transmit or receive a signal to or fromthe Internet or another communication device, for example, according toa certain protocol such as TCP/IP. Further, the communication network931 connected to the communication device 925 is configured with anetwork connected in a wired or wireless manner, and may be, forexample, the Internet, a domestic LAN, infrared ray communication, radiowave communication, satellite communication, or the like. In the presentembodiment, various kinds of information related to driving control ofthe arm unit 120 may be transmitted or received to or from an externaldevice via the communication network 931 through the communicationdevice 925.

The hardware configuration capable of implementing the functions of therobot arm apparatus 10 and the control device 20 according to anembodiment of the present disclosure has been described above. Each ofthe above components may be configured using a versatile member, and maybe configured by hardware specialized for the function of eachcomponent. Thus, the hardware configuration to be used may beappropriately changed according to a technology level when the presentembodiment is carried out. Further, although not illustrated in FIG. 13,the robot arm apparatus 10 obviously includes various kinds ofcomponents corresponding to the arm unit 120 illustrated in FIG. 6.

Further, it is possible to create a computer program for implementingthe functions of the robot arm apparatus 10 according to the presentembodiment, the control device 20, and the display device 30 and installthe computer program in a personal computer or the like. Furthermore, itis possible to provide a computer readable recording medium storing thecomputer program as well. Examples of the recording medium include amagnetic disk, an optical disc, a magneto optical disc, and a flashmemory. Further, for example, the computer program may be delivered viaa network without using the recording medium.

The virtual force calculating unit 243 calculates virtual force in theoperation related to the whole body cooperative control using thegeneralized inverse dynamics. For example, a virtual force calculationprocess performed by the virtual force calculating unit 243 may be aseries of processes described above in (5-2-2-1. Virtual forcecalculating process). The virtual force calculating unit 243 transmitsthe calculated virtual force f_(v) to the actual force calculating unit244.

The actual force calculating unit 244 calculates actual force in theoperation related to the whole body cooperative control using thegeneralized inverse dynamics. For example, an actual force calculationprocess performed by the actual force calculating unit 244 may be aseries of processes described above in (5-2-2-2. Actual forcecalculating process). The actual force calculating unit 244 transmitsthe calculated actual force (the generated torque) τ_(a) to the idealjoint control unit 250. Further, in the present embodiment, thegenerated torque τ_(a) calculated by the actual force calculating unit244 is also referred to as a “control value” or a “control torque value”to mean a control value of the joint unit 130 in the whole bodycooperative control.

The ideal joint control unit 250 performs various kinds of operationsrelated to the ideal joint control for implementing the ideal responsebased on the theoretical model. In the present embodiment, the idealjoint control unit 250 corrects influence of a disturbance on thegenerated torque τ_(a) calculated by the actual force calculating unit244, and calculates the torque command value τ for implementing theideal response of the arm unit 120. The operation process performed bythe ideal joint control unit 250 corresponds to a series of processesdescribed above in (5-2-3. Ideal joint control).

The ideal joint control unit 250 includes a disturbance estimating unit251 and a command value calculating unit 252.

The disturbance estimating unit 251 calculates the disturbanceestimation value τ_(d) based on the torque command value τ and therotational angular velocity calculated from the rotational angle qdetected by the rotational angle detecting unit 133. Here, the torquecommand value τ refers to the command value indicating the generatedtorque of the arm unit 120 that is finally transmitted to the robot armapparatus 10. As described above, the disturbance estimating unit 251has a function corresponding to the disturbance observer 620 illustratedin FIG. 8.

The command value calculating unit 252 calculates the torque commandvalue τ serving as the command value indicating torque that is generatedby the arm unit 120 and finally transmitted to the robot arm apparatus10 using the disturbance estimation value τ_(d) calculated by thedisturbance estimating unit 251. Specifically, the command valuecalculating unit 252 calculates the torque command value τ by adding thedisturbance estimation value τ_(d) calculated by the disturbanceestimating unit 251 to T^(ref) calculated from the ideal model of thejoint unit 130 expressed by Equation (12). For example, when thedisturbance estimation value τ_(d) is not calculated, the torque commandvalue τ is used as the torque target value τ^(ref). As described above,the function of the command value calculating unit 252 corresponds to afunction other than that of the disturbance observer 620 illustrated inFIG. 8.

As described above, in the ideal joint control unit 250, a series ofprocesses described above with reference to FIG. 8 is performed suchthat information is repeatedly exchanged between the disturbanceestimating unit 251 and the command value calculating unit 252. Theideal joint control unit 250 transmits the calculated torque commandvalue τ to the drive control unit 111 of the robot arm apparatus 10. Thedrive control unit 111 performs control of supplying an amount ofelectric current corresponding to the transmitted torque command value τto the motor in the actuator of the joint unit 130, controls the numberof revolutions of the motor, and controls the rotational angle and thegenerated torque of the joint unit 130.

Furthermore, according to the present embodiment, since the respective1800 a, 1800 b, . . . , 1800 f in the joint units are able to detectuser operations, it becomes possible to move the arm unit 120 byoperating any part of the arm unit 120 of the robot arm apparatus 10.Consequently, it becomes possible to move the arm unit 120 withoutholding the arm unit 120 in one's hand, such as with an operation ofpushing the arm unit 120 with one's arm or the like.

In addition, by causing each joint unit to produce a viscosity suited tothe enlargement factor (enlargement ratio) of the display device 30, itbecomes possible to raise the viscosity when the enlargement factor ishigh to make fine adjustments easier to perform, or lower the viscositywhen the enlargement factor is low to make the arm unit easier to move.Consequently, by causing the actual amount of movement of the arm unit120 to match the operator's intuitively perceived amount of force, anintuitive opposing force may be returned from the arm unit 120 to theoperator even during work performed while looking at only a wide fieldof view on the display device 30, thereby making it possible to greatlyimprove operability.

Note that although the foregoing embodiment illustrates an example ofapplying the present disclosure to a robot arm apparatus for medicaluse, the present disclosure is applicable to robot arm apparatuses for avariety of applications other than medical use.

The preferred embodiments of the present disclosure have been describedabove with reference to the accompanying drawings, whilst the presentdisclosure is not limited to the above examples, of course. A personskilled in the art may find various alterations and modifications withinthe scope of the appended claims, and it should be understood that theywill naturally come under the technical scope of the present disclosure.

For example, the above embodiment has shown an example in which a frontedge unit of an arm unit of a robot arm apparatus is an imaging unit,and a medical procedure part is photographed by the imaging unit duringsurgery as illustrated in FIG. 1, but the present embodiment is notlimited to this example. The robot arm control system 1 according to thepresent embodiment can be applied even when a robot arm apparatusincluding a different front edge unit is used for another purpose. Forexample, the front edge unit may be an endoscope or a laparoscope, andmay be any other examination device such as an ultrasonic examinationapparatus or a gastrocamera.

For example, in a medical procedure using a laparoscope, the laparoscopeis operated with the robot arm to insert the laparoscope inside thepatient's body, and treatment is performed by using forceps and anelectrosurgical instrument inserted inside the patient's body whileobserving a picture of the site of the medical procedure on a monitor byoperating the laparoscope. With such a medical procedure method, if thepractitioner were able to operate the forceps and the electrosurgicalinstrument while operating the laparoscope for observing the site of themedical procedure with the robot arm, for example, it would be possiblefor a single person to perform the medical procedure, enabling moreefficient medical procedures. However, with typical existing balancearms, from the perspective of operability, it is difficult for a singleperson to operate the forceps and the electrosurgical instrument by handand operate the laparoscope with the robot arm simultaneously. Thus,existing methods require multiple staff members, and it is typical tohave one practitioner perform the procedure while operating thelaparoscope, while another practitioner operates the forceps and theelectrosurgical instrument. However, with a robot arm apparatusaccording to the present embodiment, high operability by whole bodycooperative control is realized, as discussed above. In addition, byideal joint control, high-precision response and high stability withfewer effects such as vibration are realized. Consequently, by operatinga laparoscope for observation with a robot arm apparatus according tothe present embodiment, for example, operation of the forceps and theelectrosurgical instrument for the procedure by hand and operation ofthe laparoscope for observation by the robot arm apparatus may beperformed easily by a single practitioner.

Further, the robot arm apparatus according to the present embodiment maybe used for purposes other than medical uses. In the robot arm apparatusaccording to the present embodiment, since the high-accuracyresponsiveness and the high stability are implemented through the idealjoint control, for example, it is also possible to deal with a task suchas processing or assembly of industrial components that has to beperformed with a high degree of accuracy.

Further, the above embodiment has been described in connection with theexample in which the joint unit of the robot arm apparatus includes arotation mechanism, and rotary driving of the rotation mechanism iscontrolled such that driving of the arm unit is controlled, but thepresent embodiment is not limited to this example. For example, in therobot arm apparatus according to the present embodiment, the linkconfiguring the arm unit may have a mechanism that expands or contractsin an extension direction of the link, and the length of the link may bevariable. When the length of the link is variable, for example, drivingof the arm unit is controlled such that a desired purpose of motion isachieved by the whole body cooperative control in which expansion andcontraction of the link is considered in addition to rotation in thejoint unit.

Further, the above embodiment has been described in connection with theexample in which the degrees of freedom of the arm unit in the robot armapparatus are the 6 or more degrees of freedom, but the presentembodiment is not limited to this example. Further, the description hasproceeded with the example in which each of the plurality of joint unitsconfiguring the arm unit includes the actuator that supports the idealjoint control, but the present embodiment is not limited to thisexample. In the present embodiment, various purposes of motion can beset according to the purpose of the robot arm apparatus. Thus, as longas the set purpose of motion can be achieved, the arm unit may havefewer than 6 degrees of freedom, and some of the plurality of jointunits configuring the arm unit may be joint units having a general jointmechanism. As described above, in the present embodiment, the arm unitmay be configured to be able to achieve the purpose of motion or may beappropriately configured according to the purpose of the robot armapparatus.

Additionally, the present technology may also be configured as below.

(1)

A robot arm apparatus, including:

one or a plurality of a joint unit that joins a plurality of linksconstituting a multi-link structure;

an acquisition unit that acquires an enlargement factor of an imageimaged by an imaging unit attached to the multi-link structure; and

a driving control unit that controls driving of the joint unit based ona state of the joint unit and the enlargement factor.

(2)

The robot arm apparatus according to (1), wherein

the driving control unit controls a viscosity of driving of the jointunit according to the enlargement factor.

(3)

The robot arm apparatus according to (2), wherein

the driving control unit raises the viscosity of driving of the jointunit as the enlargement factor increases.

(4)

The robot arm apparatus according to (2), wherein

the driving control unit selects a characteristic from a plurality ofcharacteristics prescribing a relationship between the enlargementfactor and the viscosity of driving of the joint unit, and controls theviscosity of driving of the joint unit based on the selectedcharacteristic.

(5)

The robot arm apparatus according to (1), wherein

the driving control unit controls a driving velocity of the joint unitaccording to the enlargement factor.

(6)

The robot arm apparatus according to (5), wherein

the driving control unit lowers the driving velocity of the joint unitas the enlargement factor increases.

(7)

The robot arm apparatus according to (1), wherein

the driving control unit controls a driving magnitude of the joint unitaccording to the enlargement factor.

(8)

The robot arm apparatus according to (7), wherein

the driving control unit decreases the driving magnitude of the jointunit with respect to an operation, as the enlargement factor increases.

(9)

The robot arm apparatus according to any one of (1) to (8), wherein

the driving control unit controls driving of the joint unit based on thestate of the joint unit and a zoom factor by the imaging unit.

(10)

The robot arm apparatus according to (1), wherein

the enlargement factor is computed from a zoom factor by the imagingunit and distance information about the subject.

(11)

The robot arm apparatus according to any one of (1) to (10), furtherincluding:

a detecting unit that detects an operating input by an operator, whereinthe driving control unit controls driving of the joint unit when theoperating input is detected.

(12)

The robot arm apparatus according to (11), wherein

the detecting unit detects an external force acting on the multi-linkstructure as the operating input.

(13)

The robot arm apparatus according to (1), wherein

each of a plurality of the joint unit includes a joint state detectingunit that detects a state of the joint unit, and

the joint state detecting unit at least includes

-   -   a torque detecting unit that detects a generated torque in the        joint unit and an external torque applied from an outside to the        joint unit, and    -   a rotational angle detecting unit that detects a rotational        angle of the joint unit.        (14)

The robot arm apparatus according to (13), wherein

a control value and a command value are the generated torque in thejoint unit.

(15)

The robot arm apparatus according to (1), wherein

the driving control unit controls driving of the joint unit based on acontrol value for whole body cooperative control of the multi-linkstructure computed by generalized inverse dynamics using a state of themulti-link structure acquired based on a plurality of detected states ofthe joint unit, and a purpose of motion and a constraint condition ofthe multi-link structure.

(16)

The robot arm apparatus according to (15), wherein

the control value is computed based on a virtual force which is animaginary force acting to achieve the purpose of motion in an operationspace describing a relationship between a force acting on the multi-linkstructure and an acceleration produced in the multi-link structure, andalso based on an actual force computed by converting the virtual forceinto a real force for driving the joint unit based on the constraintcondition.

(17)

The robot arm apparatus according to (15), wherein

the driving control unit controls driving of the joint unit based on acommand value computed by correcting influence of a disturbance on thecontrol value.

(18)

The robot arm apparatus according to (17), wherein

the command value is computed by correcting the control value using adisturbance estimation value expressing influence of a disturbance ondriving of the joint unit estimated based on a detected state of thejoint unit.

(19)

The robot arm apparatus according to (15), wherein

the purpose of motion is an action that at least controls the state ofthe joint unit so as to cancel out gravity acting on the multi-linkstructure, and also controls the state of the joint unit so as tosupport movement of the multi-link structure in a direction of forceapplied additionally from an outside.

(20)

The robot arm apparatus according to any one of (1) to (16), wherein

the robot arm apparatus is an apparatus for medical use.

(21)

A program causing a computer to function as:

means for detecting a state of one or a plurality of a joint unit thatjoins a plurality of links constituting a multi-link structure;

means for acquiring an on-screen enlargement factor of a subject imagedby an imaging unit attached to the multi-link structure; and

means for controlling driving of the joint unit based on a state of thejoint unit and the enlargement factor.

(22)

A robot arm apparatus, including:

one or a plurality of a joint unit that joins a plurality of linksconstituting a multi-link structure; and

a driving control unit that controls a viscosity of driving of the jointunit based on a state of the joint unit.

(23)

The robot arm apparatus according to (22), further including:

an acquisition unit that acquires an on-screen enlargement factor of asubject imaged by an imaging unit attached to the multi-link structure,wherein

the driving control unit controls a viscosity of driving of the jointunit according to the enlargement factor.

(24)

The robot arm apparatus according to (23), wherein

the driving control unit raises the viscosity of driving of the jointunit as the enlargement factor increases.

(25)

The robot arm apparatus according to (23), wherein

the driving control unit selects a characteristic from a plurality ofcharacteristics prescribing a relationship between the enlargementfactor and the viscosity of driving of the joint unit, and controls theviscosity of driving of the joint unit based on the selectedcharacteristic.

(26)

The robot arm apparatus according to (22) to (25), wherein

the robot arm apparatus is an apparatus for medical use.

(27)

The robot arm apparatus according to (22), wherein

the state of the joint unit is an orientation of the multi-linkstructure.

(28)

The robot arm apparatus according to (22), wherein

the state of the joint unit is a driving velocity of the joint unit.

(29)

The robot arm apparatus according to (22), wherein

the state of the joint unit is a driving direction of the joint unit.

(30)

A robot arm apparatus control method, including:

detecting one or a plurality of a state of one or a plurality of a jointunit that joins a plurality of links constituting a multi-linkstructure;

acquiring an on-screen enlargement factor of a subject imaged by animaging unit attached to the multi-link structure; and

controlling driving of the joint unit based on a state of the joint unitand the enlargement factor.

REFERENCE SIGNS LIST

-   1 robot arm control system-   10 robot arm apparatus-   20 control device-   30 display device-   110 arm control unit-   111 drive control unit-   120 arm unit-   130 joint unit-   131 joint driving unit-   132 rotational angle detecting unit-   133 torque detecting unit-   140 imaging unit-   210 input unit-   220 storage unit-   230 control unit-   240 whole body cooperative control unit-   241 arm state acquiring unit-   242 operation condition setting unit-   243 virtual force calculating unit-   244 actual force calculating unit-   250 ideal joint control unit-   251 disturbance estimating unit-   252 command value calculating unit

1. A medical arm system, comprising: one or a plurality of a joint unitthat joins a plurality of links constituting a multi-link structure; andprocessing circuitry configured to control a resistance of rotation ofthe joint unit according to a state of the joint unit and a zoom factorof a medical imaging unit attached to the multi-link structure.
 2. Themedical arm system according to claim 1, wherein the processingcircuitry controls the resistance of rotation of the joint unitaccording to the state of the joint unit, the zoom factor of the medicalimaging unit and distance information about a distance from the medicalimaging unit to a subject.
 3. The medical arm system according to claim1, wherein the processing circuitry raises the resistance of rotation ofthe joint unit as the zoom factor increases.
 4. The medical arm systemaccording to claim 1, wherein the processing circuitry selects acharacteristic from a plurality of characteristics prescribing arelationship between the zoom factor and the resistance of rotation ofthe joint unit, and controls the resistance of rotation of the jointunit based on the selected characteristic.
 5. The medical arm systemaccording to claim 1, wherein the processing circuitry controls adriving magnitude of the joint unit according to the zoom factor.
 6. Themedical arm system according to claim 5, wherein the processingcircuitry decreases the driving magnitude of the joint unit with respectto an operation, as the zoom factor increases.
 7. The medical arm systemaccording to claim 1, wherein the processing circuitry is furtherconfigured to: detect an operating input by an operator, wherein theprocessing circuitry controls driving of the joint unit when theoperating input is detected.
 8. The medical arm system according toclaim 7, wherein the processing circuitry detects an external forceacting on the multi-link structure as the operating input.
 9. Themedical arm system according to claim 1, wherein each of a plurality ofthe joint unit includes a sensor configured to detect the state of thejoint unit, and the sensor at least includes: a torque sensor configuredto detect a generated torque in the joint unit and an external torqueapplied from an outside to the joint unit, and an encoder configured todetect a rotational angle of the joint unit.
 10. The medical arm systemaccording to claim 9, wherein a control value and a command value arethe generated torque in the joint unit.
 11. The medical arm systemaccording to claim 1, wherein the processing circuitry controls drivingof the joint unit based on a control value for whole body cooperativecontrol of the multi-link structure computed by generalized inversedynamics using a state of the multi-link structure acquired based on aplurality of detected states of the joint unit, and a purpose of motionand a constraint condition of the multi-link structure.
 12. The medicalarm system according to claim 11, wherein the control value is computedbased on a virtual force which is an imaginary force acting to achievethe purpose of motion in an operation space describing a relationshipbetween a force acting on the multi-link structure and an accelerationgenerated in the multi-link structure, and also based on an actual forcecomputed by converting the virtual force into a real force for drivingthe joint unit based on the constraint condition.
 13. The medical armsystem according to claim 11, wherein the processing circuitry controlsdriving of the joint unit based on the command value computed bycorrecting influence of a disturbance on the control value.
 14. Themedical arm system according to claim 13, wherein the command value iscomputed by correcting the control value using a disturbance estimationvalue expressing influence of a disturbance on driving of the joint unitestimated based on a detected state of the joint unit.
 15. The medicalarm system according to claim 11, wherein the purpose of motion is anaction that at least controls the state of the joint unit so as tocancel out gravity acting on the multi-link structure, and also controlsthe state of the joint unit so as to support movement of the multi-linkstructure in a direction of force applied additionally from an outside.16. The medical arm system according to claim 1, wherein the state ofthe joint unit is an orientation of the multi-link structure.
 17. Themedical arm system according to claim 1, wherein the state of the jointunit is a driving velocity of the joint unit.
 18. The medical arm systemaccording to claim 1, wherein the state of the joint unit is a drivingdirection of the joint unit.
 19. The medical arm system according toclaim 1, wherein the resistance of rotation is a viscosity of driving ofthe joint units.
 20. A non-transitory computer readable medium storing aprogram causing a computer to: detect a state of one or a plurality of ajoint unit that joins a plurality of links constituting a multi-linkstructure supporting a medical imaging unit; and control a resistance ofrotation of the joint unit according to the state of the joint unit anda zoom factor of a medical imaging unit attached to the multi-linkstructure.